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Castaing Bertrand


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2015   Références trouvées : 4

Le Meur, R., Culard, F., Nadan, V., Goffinont, S., Coste, F., Guerin, M., Loth, K., Landon, C. and Castaing, B.  (2015)

The nucleoid-associated protein HU enhances 8-oxoguanine base excision by the formamidopyrimidine-DNA glycosylase

Biochemical Journal (2015) 471 (1) 13-23 - doi : 10.1042/BJ20150387
The nucleoid-associated protein HU is involved in numerous DNA transactions and thus is essential in DNA maintenance and bacterial survival. The high affinity of HU for SSBs (single-strand breaks) has suggested its involvement in DNA protection, repair and recombination. SSB-containing DNA are major intermediates transiently generated by bifunctional DNA N-glycosylases that initiate the BER (base excision repair) pathway. Enzyme kinetics and DNA-binding experiments demonstrate that HU enhances the 8-oxoguanine-DNA glycosylase activity of Fpg (formamidopyrimidine-DNA glycosylase) by facilitating the release of the enzyme from its final DNA product (one nucleoside gap). We propose that the displacement of Fpg from its end-DNA product by HU is an active mechanism in which HU recognizes the product when it is still bound by Fpg. Through DNA binding, the two proteins interplay to form a transient ternary complex Fpg/DNA/HU which results in the release of Fpg and the molecular entrapment of SSBs by HU. These results support the involvement of HU in BER in vivo.

The nucleoid-associated protein HU is involved in numerous DNA transactions and thus is essential in DNA maintenance and bacterial survival. The high affinity of HU for SSBs (single-strand breaks) has suggested its involvement in DNA protection, repair and recombination. SSB-containing DNA are major intermediates transiently generated by bifunctional DNA N-glycosylases that initiate the BER (base excision repair) pathway. Enzyme kinetics and DNA-binding experiments demonstrate that HU enhances the 8-oxoguanine-DNA glycosylase activity of Fpg (formamidopyrimidine-DNA glycosylase) by facilitating the release of the enzyme from its final DNA product (one nucleoside gap). We propose that the displacement of Fpg from its end-DNA product by HU is an active mechanism in which HU recognizes the product when it is still bound by Fpg. Through DNA binding, the two proteins interplay to form a transient ternary complex Fpg/DNA/HU which results in the release of Fpg and the molecular entrapment of SSBs by HU. These results support the involvement of HU in BER in vivo.

D’Heygère F., Schwartz A., Coste F., Castaing B., Boudvillain M.  (2015)

ATP-dependent motor activity of the transcription termination factor Rho from Mycobacterium tuberculosis

Nucleic Acids Research (2015) First published online : May 20, 2015 - doi : 10.1093/nar/gkv505
The bacterial transcription termination factor Rho—a ring-shaped molecular motor displaying directional, ATP-dependent RNA helicase/translocase activity—is an interesting therapeutic target. Recently, Rho from Mycobacterium tuberculosis (MtbRho) has been proposed to operate by a mechanism uncoupled from molecular motor action, suggesting that the manner used by Rho to dissociate transcriptional complexes is not conserved throughout the bacterial kingdom. Here, however, we demonstrate that MtbRho is a bona fide molecular motor and directional helicase which requires a catalytic site competent for ATP hydrolysis to disrupt RNA duplexes or transcription elongation complexes. Moreover, we show that idiosyncratic features of the MtbRho enzyme are conferred by a large, hydrophilic insertion in its N-terminal ‘RNA binding’ domain and by a non-canonical R-loop residue in its C-terminal ‘motor’ domain. We also show that the ‘motor’ domain of MtbRho has a low apparent affinity for the Rho inhibitor bicyclomycin, thereby contributing to explain why M. tuberculosis is resistant to this drug. Overall, our findings support that, in spite of adjustments of the Rho motor to specific traits of its hosting bacterium, the basic principles of Rho action are conserved across species and could thus constitute pertinent screening criteria in high-throughput searches of new Rho inhibitors.

The bacterial transcription termination factor Rho—a ring-shaped molecular motor displaying directional, ATP-dependent RNA helicase/translocase activity—is an interesting therapeutic target. Recently, Rho from Mycobacterium tuberculosis (MtbRho) has been proposed to operate by a mechanism uncoupled from molecular motor action, suggesting that the manner used by Rho to dissociate transcriptional complexes is not conserved throughout the bacterial kingdom. Here, however, we demonstrate that MtbRho is a bona fide molecular motor and directional helicase which requires a catalytic site competent for ATP hydrolysis to disrupt RNA duplexes or transcription elongation complexes. Moreover, we show that idiosyncratic features of the MtbRho enzyme are conferred by a large, hydrophilic insertion in its N-terminal ‘RNA binding’ domain and by a non-canonical R-loop residue in its C-terminal ‘motor’ domain. We also show that the ‘motor’ domain of MtbRho has a low apparent affinity for the Rho inhibitor bicyclomycin, thereby contributing to explain why M. tuberculosis is resistant to this drug. Overall, our findings support that, in spite of adjustments of the Rho motor to specific traits of its hosting bacterium, the basic principles of Rho action are conserved across species and could thus constitute pertinent screening criteria in high-throughput searches of new Rho inhibitors.

D’Heygère F., Schwartz A., Coste F., Castaing B., Boudvillain M.  (2015)

Monitoring RNA Unwinding by the Transcription Termination Factor Rho from Mycobacterium tuberculosis

In "RNA Remodeling Proteins" (2015) vol. 1259, chap 18, 293-311 - doi : 10.1007/978-1-4939-2214-7_18
Transcription termination factor Rho is a ring-shaped, homo-hexamieric RNA translocase that dissociates transcription elongation complexes and transcriptional RNA-DNA duplexes (R-loops) in bacteria. The molecular mechanisms underlying these biological functions have been essentially studied with Rho enzymes from Escherichia coli or close Gram-negative relatives. However, phylo-divergent Rho factors may have distinct properties. Here, we describe methods for the preparation and in vitro characterization (ATPase and helicase activities) of the Rho factor from Mycobacterium tuberculosis, a specimen with uncharacteristic molecular and enzymatic features. These methods set the stage for future studies aimed at better defining the diversity of enzymatic properties of Rho across the bacterial kingdom.

Transcription termination factor Rho is a ring-shaped, homo-hexamieric RNA translocase that dissociates transcription elongation complexes and transcriptional RNA-DNA duplexes (R-loops) in bacteria. The molecular mechanisms underlying these biological functions have been essentially studied with Rho enzymes from Escherichia coli or close Gram-negative relatives. However, phylo-divergent Rho factors may have distinct properties. Here, we describe methods for the preparation and in vitro characterization (ATPase and helicase activities) of the Rho factor from Mycobacterium tuberculosis, a specimen with uncharacteristic molecular and enzymatic features. These methods set the stage for future studies aimed at better defining the diversity of enzymatic properties of Rho across the bacterial kingdom.

Le Meur R., Loth K. Culard F., Castaing B., Landon C.  (2015)

Backbone assignment of the three dimers of HU from Escherichia coli at 293 K : EcHUα2, EcHUβ2 and EcHUαβ

Biomolecular NMR Assignments (2015) 1-5 - doi : 10.1007/s12104-015-9610-6
HU is one of the major nucleoid-associated proteins involved in bacterial chromosome structure and in all DNA-dependent cellular activities. Similarly to eukaryotic histones, this small dimeric basic protein wraps DNA in a non-sequence specific manner, promoting DNA super-structures. In most bacteria, HU is a homodimeric protein encoded by a single gene. However, in enterobacteria such as Escherichia coli, the presence of two genes coding for two peptidic chains, HUα and HUβ, lead to the coexistence of three forms : two homodimers EcHUα2 and EcHUβ2, as well as a heterodimer EcHUαβ. Genetic and biochemical investigation suggest that each EcHU dimer plays a specific physiological role in bacteria. Their relative abundance depends on the environmental conditions and is driven by an essential, yet unknown, fast outstanding chain-exchange mechanism at physiological temperature. Our goal is to understand this fundamental mechanism from a structural and kinetics standpoint using NMR. For this purpose, the first steps are the assignment of each dimer in their native and intermediate states. Here, we report the backbone assignment of each HU dimers from E. coli at 293 K in their native state.

HU is one of the major nucleoid-associated proteins involved in bacterial chromosome structure and in all DNA-dependent cellular activities. Similarly to eukaryotic histones, this small dimeric basic protein wraps DNA in a non-sequence specific manner, promoting DNA super-structures. In most bacteria, HU is a homodimeric protein encoded by a single gene. However, in enterobacteria such as Escherichia coli, the presence of two genes coding for two peptidic chains, HUα and HUβ, lead to the coexistence of three forms : two homodimers EcHUα2 and EcHUβ2, as well as a heterodimer EcHUαβ. Genetic and biochemical investigation suggest that each EcHU dimer plays a specific physiological role in bacteria. Their relative abundance depends on the environmental conditions and is driven by an essential, yet unknown, fast outstanding chain-exchange mechanism at physiological temperature. Our goal is to understand this fundamental mechanism from a structural and kinetics standpoint using NMR. For this purpose, the first steps are the assignment of each dimer in their native and intermediate states. Here, we report the backbone assignment of each HU dimers from E. coli at 293 K in their native state.


2014   Références trouvées : 2

Biela, A., Coste, F., Culard, F., Guerin, M., Goffinont, S. Gasteiger, K., Cieśla, J., Winczura, A., Kazimierczuk, Z., Gasparutto, D., Carell, T., Tudek, B., Castaing, B.  (2014)

Zinc finger oxidation of Fpg/Nei DNA glycosylases by 2-thioxanthine : biochemical and X-ray structural characterization

Nucleic Acids Research (2014) 42(16) 10748-10761 - doi : 10.1093/nar/gku613
DNA glycosylases from the Fpg/Nei structural superfamily are base excision repair enzymes involved in the removal of a wide variety of mutagen and potentially lethal oxidized purines and pyrimidines. Although involved in genome stability, the recent discovery of synthetic lethal relationships between DNA glycosylases and other pathways highlights the potential of DNA glycosylase inhibitors for future medicinal chemistry development in cancer therapy. By combining biochemical and structural approaches, the physical target of 2-thioxanthine (2TX), an uncompetitive inhibitor of Fpg, was identified. 2TX interacts with the zinc finger (ZnF) DNA binding domain of the enzyme. This explains why the zincless hNEIL1 enzyme is resistant to 2TX. Crystal structures of the enzyme bound to DNA in the presence of 2TX demonstrate that the inhibitor chemically reacts with cysteine thiolates of ZnF and induces the loss of zinc. The molecular mechanism by which 2TX inhibits Fpg may be generalized to all prokaryote and eukaryote ZnF-containing Fpg/Nei-DNA glycosylases. Cell experiments show that 2TX can operate in cellulo on the human Fpg/Nei DNA glycosylases. The atomic elucidation of the determinants for the interaction of 2TX to Fpg provides the foundation for the future design and synthesis of new inhibitors with high efficiency and selectivity.

DNA glycosylases from the Fpg/Nei structural superfamily are base excision repair enzymes involved in the removal of a wide variety of mutagen and potentially lethal oxidized purines and pyrimidines. Although involved in genome stability, the recent discovery of synthetic lethal relationships between DNA glycosylases and other pathways highlights the potential of DNA glycosylase inhibitors for future medicinal chemistry development in cancer therapy. By combining biochemical and structural approaches, the physical target of 2-thioxanthine (2TX), an uncompetitive inhibitor of Fpg, was identified. 2TX interacts with the zinc finger (ZnF) DNA binding domain of the enzyme. This explains why the zincless hNEIL1 enzyme is resistant to 2TX. Crystal structures of the enzyme bound to DNA in the presence of 2TX demonstrate that the inhibitor chemically reacts with cysteine thiolates of ZnF and induces the loss of zinc. The molecular mechanism by which 2TX inhibits Fpg may be generalized to all prokaryote and eukaryote ZnF-containing Fpg/Nei-DNA glycosylases. Cell experiments show that 2TX can operate in cellulo on the human Fpg/Nei DNA glycosylases. The atomic elucidation of the determinants for the interaction of 2TX to Fpg provides the foundation for the future design and synthesis of new inhibitors with high efficiency and selectivity.

Paquet F., Delalande O., Goffinont S., Culard F., Loth K., Asseline U., Castaing B. and Landon C.  (2014)

Model of a DNA-Protein Complex of the Architectural Monomeric Protein MC1 from Euryarchaea

PLoS ONE 9 (2) e88809 - doi : 10.1371/journal.pone.0088809
In Archaea the two major modes of DNA packaging are wrapping by histone proteins or bending by architectural non-histone proteins. To supplement our knowledge about the binding mode of the different DNA-bending proteins observed across the three domains of life, we present here the first model of a complex in which the monomeric Methanogen Chromosomal protein 1 (MC1) from Euryarchaea binds to the concave side of a strongly bent DNA. In laboratory growth conditions MC1 is the most abundant architectural protein present in Methanosarcina thermophila CHTI55. Like most proteins that strongly bend DNA, MC1 is known to bind in the minor groove. Interaction areas for MC1 and DNA were mapped by Nuclear Magnetic Resonance (NMR) data. The polarity of protein binding was determined using paramagnetic probes attached to the DNA. The first structural model of the DNA-MC1 complex we propose here was obtained by two complementary docking approaches and is in good agreement with the experimental data previously provided by electron microscopy and biochemistry. Residues essential to DNA-binding and -bending were highlighted and confirmed by site-directed mutagenesis. It was found that the Arg25 side-chain was essential to neutralize the negative charge of two phosphates that come very close in response to a dramatic curvature of the DNA.

In Archaea the two major modes of DNA packaging are wrapping by histone proteins or bending by architectural non-histone proteins. To supplement our knowledge about the binding mode of the different DNA-bending proteins observed across the three domains of life, we present here the first model of a complex in which the monomeric Methanogen Chromosomal protein 1 (MC1) from Euryarchaea binds to the concave side of a strongly bent DNA. In laboratory growth conditions MC1 is the most abundant architectural protein present in Methanosarcina thermophila CHTI55. Like most proteins that strongly bend DNA, MC1 is known to bind in the minor groove. Interaction areas for MC1 and DNA were mapped by Nuclear Magnetic Resonance (NMR) data. The polarity of protein binding was determined using paramagnetic probes attached to the DNA. The first structural model of the DNA-MC1 complex we propose here was obtained by two complementary docking approaches and is in good agreement with the experimental data previously provided by electron microscopy and biochemistry. Residues essential to DNA-binding and -bending were highlighted and confirmed by site-directed mutagenesis. It was found that the Arg25 side-chain was essential to neutralize the negative charge of two phosphates that come very close in response to a dramatic curvature of the DNA.


2012   Références trouvées : 2

Matot, B. ; Le Bihan, Y.-V. ; Lescasse, R. ; Pérez, J. ; Miron, S. ; David, G. ; Castaing, B. ; Weber, P. ; Raynal, B. ; Zinn-Justin, S. ; Gasparini, S. and Le Du, M.-H.  (2012)

The orientation of the C-terminal domain of the Saccharomyces cerevisiae Rap1 protein is determined by its binding to DNA

Nucleic Acids Res. 40 (7) 3197-3207
Rap1 is an essential DNA-binding factor from the yeast Saccharomyces cerevisiae involved in transcription and telomere maintenance. Its binding to DNA targets Rap1 at particular loci, and may optimize its ability to form functional macromolecular assemblies. It is a modular protein, rich in large potentially unfolded regions, and comprising BRCT, Myb and RCT well-structured domains. Here, we present the architectures of Rap1 and a Rap1/DNA complex, built through a step-by-step integration of small angle X-ray scattering, X-ray crystallography and nuclear magnetic resonance data. Our results reveal Rap1 structural adjustment upon DNA binding that involves a specific orientation of the C-terminal (RCT) domain with regard to the DNA binding domain (DBD). Crystal structure of DBD in complex with a long DNA identifies an essential wrapping loop, which constrains the orientation of the RCT and affects Rap1 affinity to DNA. Based on our structural information, we propose a model for Rap1 assembly at telomere.

Rap1 is an essential DNA-binding factor from the yeast Saccharomyces cerevisiae involved in transcription and telomere maintenance. Its binding to DNA targets Rap1 at particular loci, and may optimize its ability to form functional macromolecular assemblies. It is a modular protein, rich in large potentially unfolded regions, and comprising BRCT, Myb and RCT well-structured domains. Here, we present the architectures of Rap1 and a Rap1/DNA complex, built through a step-by-step integration of small angle X-ray scattering, X-ray crystallography and nuclear magnetic resonance data. Our results reveal Rap1 structural adjustment upon DNA binding that involves a specific orientation of the C-terminal (RCT) domain with regard to the DNA binding domain (DBD). Crystal structure of DBD in complex with a long DNA identifies an essential wrapping loop, which constrains the orientation of the RCT and affects Rap1 affinity to DNA. Based on our structural information, we propose a model for Rap1 assembly at telomere.

Baucheron, S., Coste, F., Canepa, S., Maurel, M.C., Giraud, E., Culard, F., Castaing, B., Roussel, A. and Cloeckaert, A.  (2012)

Binding of the RamR Repressor to Wild-Type and Mutated Promoters of the ramA Gene Involved in Efflux-Mediated Multidrug Resistance in Salmonella enterica Serovar Typhimurium

Antimicrob Agents Chemother. 56 (2) 942-948
The transcriptional activator RamA is involved in multidrug resistance (MDR) by increasing expression of the AcrAB-TolC RND-type efflux system in several pathogenic Enterobacteriaceae. In Salmonella enterica serovar Typhimurium (S. Typhimurium), ramA expression is negatively regulated at the local level by RamR, a transcriptional repressor of the TetR family. We here studied the DNA-binding activity of the RamR repressor with the ramA promoter (P(ramA)). As determined by high-resolution footprinting, the 28-bp-long RamR binding site covers essential features of P(ramA), including the -10 conserved region, the transcriptional start site of ramA, and two 7-bp inverted repeats. Based on the RamR footprint and on electrophoretic mobility shift assays (EMSAs), we propose that RamR interacts with P(ramA) as a dimer of dimers, in a fashion that is structurally similar to the QacR-DNA binding model. Surface plasmon resonance (SPR) measurements indicated that RamR has a 3-fold-lower affinity (K(D) [equilibrium dissociation constant] = 191 nM) for the 2-bp-deleted P(ramA) of an MDR S. Typhimurium clinical isolate than for the wild-type P(ramA) (K(D) = 66 nM). These results confirm the direct regulatory role of RamR in the repression of ramA transcription and precisely define how an alteration of its binding site can give rise to an MDR phenotype.

The transcriptional activator RamA is involved in multidrug resistance (MDR) by increasing expression of the AcrAB-TolC RND-type efflux system in several pathogenic Enterobacteriaceae. In Salmonella enterica serovar Typhimurium (S. Typhimurium), ramA expression is negatively regulated at the local level by RamR, a transcriptional repressor of the TetR family. We here studied the DNA-binding activity of the RamR repressor with the ramA promoter (P(ramA)). As determined by high-resolution footprinting, the 28-bp-long RamR binding site covers essential features of P(ramA), including the -10 conserved region, the transcriptional start site of ramA, and two 7-bp inverted repeats. Based on the RamR footprint and on electrophoretic mobility shift assays (EMSAs), we propose that RamR interacts with P(ramA) as a dimer of dimers, in a fashion that is structurally similar to the QacR-DNA binding model. Surface plasmon resonance (SPR) measurements indicated that RamR has a 3-fold-lower affinity (K(D) [equilibrium dissociation constant] = 191 nM) for the 2-bp-deleted P(ramA) of an MDR S. Typhimurium clinical isolate than for the wild-type P(ramA) (K(D) = 66 nM). These results confirm the direct regulatory role of RamR in the repression of ramA transcription and precisely define how an alteration of its binding site can give rise to an MDR phenotype.


2011   Références trouvées : 1

Garnier, N., Loth, K., Coste, F. Augustyniak, R., Nadan, V., Damblon, C. & Castaing, B..  (2011)

An alternative flexible conformation of the E. coli HUβ(2) protein : structural, dynamics, and functional aspects.

European Biophysics Journal 40 (2) 117-129
The histone-like HU protein is the major nucleoid-associated protein involved in the dynamics and structure of the bacterial chromosome. Under physiological conditions, the three possible dimeric forms of the E. coli HU protein (EcHUα₂, EcHUβ₂, and EcHUαβ) are in thermal equilibrium between two dimeric conformations (N₂ ↔ I₂) varying in their secondary structure content. High-temperature molecular dynamics simulations combined with NMR experiments provide information about structural and dynamics features at the atomic level for the N₂ to I₂ thermal transition of the EcHUβ₂ homodimer. On the basis of these data, a realistic 3D model is proposed for the major I₂ conformation of EcHUβ₂. This model is in agreement with previous experimental data.

The histone-like HU protein is the major nucleoid-associated protein involved in the dynamics and structure of the bacterial chromosome. Under physiological conditions, the three possible dimeric forms of the E. coli HU protein (EcHUα₂, EcHUβ₂, and EcHUαβ) are in thermal equilibrium between two dimeric conformations (N₂ ↔ I₂) varying in their secondary structure content. High-temperature molecular dynamics simulations combined with NMR experiments provide information about structural and dynamics features at the atomic level for the N₂ to I₂ thermal transition of the EcHUβ₂ homodimer. On the basis of these data, a realistic 3D model is proposed for the major I₂ conformation of EcHUβ₂. This model is in agreement with previous experimental data.


2008   Références trouvées : 2

Coste, F ; Ober, M ; Le Bihan, YV ; Izquierdo, M ; Hervouet, N ; Mueller, H ; Carell, T ; Castaing, B   (2008)

Bacterial base excision repair enzyme Fpg (MutM) recognizes bulky N7-substituted-FapydG lesion using a novel and unproductive binding mode

Chemistry and Biology 15 (7) 706-717

Gutsche, I ; Vujicic-Žagar, A ; Siebert, X ; Servant, P ; Vannier, F ; Castaing, B ; Gallet, B ; Heulin, T ; de Groot, A ; Sommer, S ; Serre, L   (2008)

Complex oligomeric structure of a truncated form of DdrA : a protein required for the extreme radiotolerance of Deinococcus

Biochimica et Biophysica Acta 1784 (7-8) 1050-1058


2006   Références trouvées : 3

Davidkova, M ; Stisova, V ; Goffinont, S ; Gillard, N ; Castaing, B ; Spotheim-Maurizot, M  (2006)

Modification of DNA radiolysis by DNA-binding proteins : structural aspects

Radiation Protection Dosimetry 122 (1-4) 100-105
Formation of specific complexes between proteins and their cognate DNA modulates the yields and the location of radiation damage on both partners of the complex. The radiolysis of DNA-protein complexes is studied for : (1) the Escherichia coli lactose operator-repressor complex, (2) the complex between DNA bearing an analogue of an abasic site and the repair protein Fpg of Lactococcus lactis. Experimental patterns of DNA damages are presented and compared to predicted damage distribution obtained using an improved version of the stochastic model RADACK. The same method is used for predicting the location of damages on the proteins. At doses lower than a threshold that depends on the system, proteins protect their specific binding site on DNA while at high doses, the studied complexes are disrupted mainly through protein damage. The loss of binding ability is the functional consequence of the amino-acids modification by OH radicals. Many of the most probably damaged amino acids are essential for the DNA-protein interaction and within a complex are protected by DNA.

Formation of specific complexes between proteins and their cognate DNA modulates the yields and the location of radiation damage on both partners of the complex. The radiolysis of DNA-protein complexes is studied for : (1) the Escherichia coli lactose operator-repressor complex, (2) the complex between DNA bearing an analogue of an abasic site and the repair protein Fpg of Lactococcus lactis. Experimental patterns of DNA damages are presented and compared to predicted damage distribution obtained using an improved version of the stochastic model RADACK. The same method is used for predicting the location of damages on the proteins. At doses lower than a threshold that depends on the system, proteins protect their specific binding site on DNA while at high doses, the studied complexes are disrupted mainly through protein damage. The loss of binding ability is the functional consequence of the amino-acids modification by OH radicals. Many of the most probably damaged amino acids are essential for the DNA-protein interaction and within a complex are protected by DNA.

Bure, C ; Castaing, B ; Lange, C ; Delmas, AF  (2006)

Location and base selectivity on fragmentation of brominated oligodeoxynucleotides

Journal of Mass Spectrometry 41 (1) 84-90
Bromine-modified oligodeoxynucleotides (ODNs) were fragmented in the electrospray source to study the influence of brominated bases on fragmentation. Several 13-mer ODNs containing a brominated pyrimidine base, BrdU (5-bromodeoxyuridine) or BrdC (5-bromodeoxycytidine), were analyzed. Low cone voltage fragmentation yields a loss of the brominated base with a preferential loss for the brominated base closer to the 5-end (2-position > 4-position > 12-position) as well as a preferential loss of BrdU over BrdC. Higher cone voltage produces backbone fragmentation with complementary a(n)-base and w(m) ions close to the brominated base. On the basis of these observations, we located the brominated base in the sequence for all of the ODNs studied. Copyright (c) 2005 John Wiley & Sons, Ltd.

Bromine-modified oligodeoxynucleotides (ODNs) were fragmented in the electrospray source to study the influence of brominated bases on fragmentation. Several 13-mer ODNs containing a brominated pyrimidine base, BrdU (5-bromodeoxyuridine) or BrdC (5-bromodeoxycytidine), were analyzed. Low cone voltage fragmentation yields a loss of the brominated base with a preferential loss for the brominated base closer to the 5-end (2-position > 4-position > 12-position) as well as a preferential loss of BrdU over BrdC. Higher cone voltage produces backbone fragmentation with complementary a(n)-base and w(m) ions close to the brominated base. On the basis of these observations, we located the brominated base in the sequence for all of the ODNs studied. Copyright (c) 2005 John Wiley & Sons, Ltd.

Boiteux, S ; Castaing, B ; Radicella, PJ  (2006)

BER : (Base excision repair) : molecular mechanisms and biological roles

Biofutur (271) 35-39


2005   Références trouvées : 3

Begusova, M ; Gillard, N ; Sy, D ; Castaing, B ; Charlier, M ; Spotheim-Maurizot, M  (2005)

Radiolysis of DNA-protein complexes

Radiation Physics and Chemistry 72 (2-3) 265-270
We discuss here modifications of DNA and protein radiolysis due to the interaction of the-se two partners in specific complexes. Experimental patterns of frank strand breaks (FSB) and alkali revealed breaks (ARB) obtained for DNNA lac operator bound to the lac repressor and for a DNA containing an abasic site analog bound to the formamidopyrimidine-DNA glycosylase are reported. Experimental data are compared to predicted damage distribution obtained using the theoretical model RADACK. (C) 2004 Elsevier Ltd. All rights reserved.

We discuss here modifications of DNA and protein radiolysis due to the interaction of the-se two partners in specific complexes. Experimental patterns of frank strand breaks (FSB) and alkali revealed breaks (ARB) obtained for DNNA lac operator bound to the lac repressor and for a DNA containing an abasic site analog bound to the formamidopyrimidine-DNA glycosylase are reported. Experimental data are compared to predicted damage distribution obtained using the theoretical model RADACK. (C) 2004 Elsevier Ltd. All rights reserved.

de Jesus, KP ; Serre, L ; Zelwer, C ; Castaing, B  (2005)

Structural insights into abasic site for Fpg specific binding and catalysis : comparative high-resolution crystallographic studies of Fpg bound to various models of abasic site analogues-containing DNA

Nucleic Acids Research 33 (18) 5936-5944
dFpg is a DNA glycosylase that recognizes and excises the mutagenic 8-oxoguanine (8-oxoG) and the potentially lethal formamidopyrimidic residues (Fapy). Fpg is also associated with an AP lyase activity which successively cleaves the abasic (AP) site at the 3' and 5' sides by ß delta-elimination. Here, we present the high-resolution crystal structures of the wild-type and the P1G defective mutant of Fpg from Lactococcus lactis bound to 14mer DNA duplexes containing either a tetrahydrofuran (THF) or 1,3-propanediol (Pr) AP site analogues.

dFpg is a DNA glycosylase that recognizes and excises the mutagenic 8-oxoguanine (8-oxoG) and the potentially lethal formamidopyrimidic residues (Fapy). Fpg is also associated with an AP lyase activity which successively cleaves the abasic (AP) site at the 3’ and 5’ sides by ß delta-elimination. Here, we present the high-resolution crystal structures of the wild-type and the P1G defective mutant of Fpg from Lactococcus lactis bound to 14mer DNA duplexes containing either a tetrahydrofuran (THF) or 1,3-propanediol (Pr) AP site analogues.

Ober, M ; Hsu, GW ; Beese, LS ; Coste, F ; Boiteux, S ; Zelwer, C ; Castaing, B ; Carell, T  (2005)

Replication and repair of the oxidative DNA lesions 8-oxoG and FaPyG

Abstracts of Papers of The American Chemical Society 229 U260-U260 Part 1


2004   Références trouvées : 3

Gillard, N ; Begusova, M ; Castaing, B ; Spotheim-Maurizot, M  (2004)

Radiation affects binding of Fpg repair protein to an abasic site containing DNA

Radiation Research 162 (5) 566-571
During the base excision repair of certain DNA lesions, the formamidopyrimidine-DNA glycosylase (Fpg) binds specifically to the DNA region containing an abasic (AP) site. Is this step affected by exposure to ionizing radiation ? To answer this question, we studied a complex between a DNA duplex containing an analogue of an abasic site (the 1,3-propanediol site, Pr) and a mutated Lactococcus lactis Fpg (PIG-LlFpg) lacking strand cleavage activity. Upon irradiation of the complex, the ratio of bound/free partners decreased. When the partners were irradiated separately, the irradiated DNA still bound the unirradiated protein, whereas irradiated Fpg no longer bound unirradiated DNA.

During the base excision repair of certain DNA lesions, the formamidopyrimidine-DNA glycosylase (Fpg) binds specifically to the DNA region containing an abasic (AP) site. Is this step affected by exposure to ionizing radiation ? To answer this question, we studied a complex between a DNA duplex containing an analogue of an abasic site (the 1,3-propanediol site, Pr) and a mutated Lactococcus lactis Fpg (PIG-LlFpg) lacking strand cleavage activity. Upon irradiation of the complex, the ratio of bound/free partners decreased. When the partners were irradiated separately, the irradiated DNA still bound the unirradiated protein, whereas irradiated Fpg no longer bound unirradiated DNA.

Coste, F ; Ober, M ; Carell, T ; Boiteux, S ; Zelwer, C ; Castaing, B  (2004)

Structural basis for the recognition of the FapydG lesion (2,6-diamino-4-hydroxy-5-formamidopyrimidine) by formamidopyrimidine-DNA glycosylase

Journal of Biological Chemistry 279 (42) 44074-44083
Formamidopyrimidine-DNA glycosylase (Fpg) is a DNA repair enzyme that excises oxidized purines such as 7,8-dihydro-8-oxoguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG) from damaged DNA. Here, we report the crystal structure of the Fpg protein from Lactococcus lactis (LlFpg) bound to a carbocyclic FapydG (cFapydG)-containing DNA.

Formamidopyrimidine-DNA glycosylase (Fpg) is a DNA repair enzyme that excises oxidized purines such as 7,8-dihydro-8-oxoguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG) from damaged DNA. Here, we report the crystal structure of the Fpg protein from Lactococcus lactis (LlFpg) bound to a carbocyclic FapydG (cFapydG)-containing DNA.

Amara, P ; Serre, L ; Castaing, B ; Thomas, A  (2004)

Insights into the DNA repair process by the formamidopyrimidine-DNA glycosylase investigated by molecular dynamics

Protein Science 13 (8) 2009-2021
Formamidopyrimidine-DNA glycosylase (Fpg) identifies and removes 8-oxoguanine from DNA. All of the X-ray structures of Fpg complexed to an abasic site containing DNA exhibit a common disordered region present in the C-terminal domain of the enzyme. However, this region is believed to be involved in the damaged base binding site when the initial protein/DNA complex is formed. The dynamic behavior of the disordered polypeptide (named Loop) in relation to the supposed scenario for the DNA repair mechanism was investigated by molecular dynamics on different models, derived from the X-ray structure of Lactococcus lactis Fpg bound to an abasic site analog-containing DNA and of Bacillus stearothermophilus Fpg bound to 8-oxoG.

Formamidopyrimidine-DNA glycosylase (Fpg) identifies and removes 8-oxoguanine from DNA. All of the X-ray structures of Fpg complexed to an abasic site containing DNA exhibit a common disordered region present in the C-terminal domain of the enzyme. However, this region is believed to be involved in the damaged base binding site when the initial protein/DNA complex is formed. The dynamic behavior of the disordered polypeptide (named Loop) in relation to the supposed scenario for the DNA repair mechanism was investigated by molecular dynamics on different models, derived from the X-ray structure of Lactococcus lactis Fpg bound to an abasic site analog-containing DNA and of Bacillus stearothermophilus Fpg bound to 8-oxoG.


2003   Références trouvées : 2

Muller, E ; Gasparutto, D ; Castaing, B ; Favier, A ; Cadet, J  (2003)

Recognition of cyclonucleoside lesions by the Lactococcus lactis FPG protein

Nucleosides Nucleotides & Nucleic Acids 22 (5-8) 1563-1565
Several purine and pyrimidine cyclonucleosides were found to be not recognized by several Escherichia coli and yeast DNA N-glycosylases. Interestingly, a non covalent complex was observed between the Lactoccocus lactis formamido-pyrimidine-DNA glycosylases (Fpg-L1) and the cyclonucleosides. This may provide new information on the mechanism involved in the activity of the latter enzyme.

Several purine and pyrimidine cyclonucleosides were found to be not recognized by several Escherichia coli and yeast DNA N-glycosylases. Interestingly, a non covalent complex was observed between the Lactoccocus lactis formamido-pyrimidine-DNA glycosylases (Fpg-L1) and the cyclonucleosides. This may provide new information on the mechanism involved in the activity of the latter enzyme.

Ramstein, J ; Hervouet, N ; Coste, F ; Zelwer, C ; Oberto, J ; Castaing, B  (2003)

Evidence of a thermal unfolding dimeric intermediate for the Escherichia coli histone-like HU proteins : Thermodynamics and structure

Journal of Molecular Biology 331 (1) 101-121
The Escherichia coli histone-like HU protein pool is composed of three dimeric forms : two homodimers, EcHUa(2) and EcHUß(2), and a heterodimer, EcHUaß. The relative abundance of these dimeric forms varies during cell growth and in response to environmental changes, suggesting that each dimer plays different physiological roles.

The Escherichia coli histone-like HU protein pool is composed of three dimeric forms : two homodimers, EcHUa(2) and EcHUß(2), and a heterodimer, EcHUaß. The relative abundance of these dimeric forms varies during cell growth and in response to environmental changes, suggesting that each dimer plays different physiological roles.


2002   Références trouvées : 2

de Jesus, KP ; Serre, L ; Hervouet, N ; Bouckson-Castaing, V ; Zelwer, C ; Castaing, B  (2002)

Crystallization and preliminary X-ray crystallographic studies of a complex between the Lactococcus lactis Fpg DNA-repair enzyme and an abasic site containing DNA

Acta Crystallographica Section D-Biological Crystallography 58 679-682 Part 4
For protein-DNA complex crystallization, the choice of the DNA fragment is crucial. With the aim of crystallizing the 31 kDa Fpg DNA-repair enzyme bound to DNA, oligonucleotide duplexes varying in length, sequence, end type and nature of the specific DNA target site were used. Crystals of several protein-DNA combinations grew from solutions containing both polyethylene glycol and salt. This systematic crystallization screening followed by optimization of the crystallization conditions by microseeding led to crystals of Fpg bound to a 13 base-pair duplex DNA carrying the 1,3-propanediol abasic site analogue which are suitable for crystallographic analysis. Complete native data sets have been collected to 2.1 Angstrom resolution.

For protein-DNA complex crystallization, the choice of the DNA fragment is crucial. With the aim of crystallizing the 31 kDa Fpg DNA-repair enzyme bound to DNA, oligonucleotide duplexes varying in length, sequence, end type and nature of the specific DNA target site were used. Crystals of several protein-DNA combinations grew from solutions containing both polyethylene glycol and salt. This systematic crystallization screening followed by optimization of the crystallization conditions by microseeding led to crystals of Fpg bound to a 13 base-pair duplex DNA carrying the 1,3-propanediol abasic site analogue which are suitable for crystallographic analysis. Complete native data sets have been collected to 2.1 Angstrom resolution.

Serre, L ; de Jesus, KP ; Boiteux, S ; Zelwer, C ; Castaing, B  (2002)

Crystal structure of the Lactococcus lactis formamidopyrimidine-DNA glycosylase bound to an abasic site analogue-containing DNA

Embo Journal 21 (12) 2854-2865
The formamidopyrimidine-DNA glycosylase (Fpg, MutM) is a bifunctional base excision repair enzyme (DNA glycosylase/AP lyase) that removes a wide range of oxidized purines, such as 8-oxoguanine and imidazole ring-opened purines, from oxidatively damaged DNA. The structure of a non-covalent complex between the Lactoccocus lactis Fpg and a 1,3-propanediol (Pr) abasic site analogue-containing DNA has been solved. Through an asymmetric interaction along the damaged strand and the intercalation of the triad (M75/R109/F111), Fpg pushes out the Pr site from the DNA double helix, recognizing the cytosine opposite the lesion and inducing a 60degrees bend of the DNA.

The formamidopyrimidine-DNA glycosylase (Fpg, MutM) is a bifunctional base excision repair enzyme (DNA glycosylase/AP lyase) that removes a wide range of oxidized purines, such as 8-oxoguanine and imidazole ring-opened purines, from oxidatively damaged DNA. The structure of a non-covalent complex between the Lactoccocus lactis Fpg and a 1,3-propanediol (Pr) abasic site analogue-containing DNA has been solved. Through an asymmetric interaction along the damaged strand and the intercalation of the triad (M75/R109/F111), Fpg pushes out the Pr site from the DNA double helix, recognizing the cytosine opposite the lesion and inducing a 60degrees bend of the DNA.


2000   Références trouvées : 1

Guibourt, N ; Castaing, B ; Van Der Kemp, PA ; Boiteux, S  (2000)

Catalytic and DNA binding properties of the Ogg1 protein of Saccharomyces cerevisiae : Comparison between the wild type and the K241R and K241Q active-site mutant proteins

Biochemistry 39 (7) 1716-1724
The Ogg1 protein of Saccharomyces cerevisiae belongs to a family of DNA glycosylases and apurinic/apyrimidinic site (AP) lyases, the signature of which is the a-helix-hairpin-a-helix-Gly/Pro-Asp (HhH-GPD) active site motif together with a conserved catalytic lysine residue, to which we refer as the HhH-GPD/K family. In the yeast Ogg1 protein, yOgg1, the HhH-GPD/K motif spans residues 225-260 and the conserved lysine is K241. In this study, we have purified the K241R and K241Q mutant proteins and compared their catalytic and DNA binding properties to that of the wild-type yOgg1. The results show that the K241R mutation greatly impairs both the DNA glycosylase and the AP lyase activities of yOgg1.

The Ogg1 protein of Saccharomyces cerevisiae belongs to a family of DNA glycosylases and apurinic/apyrimidinic site (AP) lyases, the signature of which is the a-helix-hairpin-a-helix-Gly/Pro-Asp (HhH-GPD) active site motif together with a conserved catalytic lysine residue, to which we refer as the HhH-GPD/K family. In the yeast Ogg1 protein, yOgg1, the HhH-GPD/K motif spans residues 225-260 and the conserved lysine is K241. In this study, we have purified the K241R and K241Q mutant proteins and compared their catalytic and DNA binding properties to that of the wild-type yOgg1. The results show that the K241R mutation greatly impairs both the DNA glycosylase and the AP lyase activities of yOgg1.


1999   Références trouvées : 3

Castaing, B ; Fourrey, JL ; Hervouet, N ; Thomas, M ; Boiteux, S ; Zelwer, C  (1999)

AP site structural determinants for Fpg specific recognition

Nucleic Acids Research 27 (2) 608-615
The binding of Escherichia coli and Lactococcus lactis Fapy-DNA glyosylase (Fpg) proteins to DNA containing either cyclic or non-cyclic abasic (AP) site analogs was investigated by electrophoretic mobility shift assay (EMSA) and by footprinting experiments. We showed that the reduced AP site is the best substrate analog for the E. coli and L. lactis enzymes (K-Dapp = 0.26 and 0.5 nM, respectively) as compared with the other analogs tested in this study (K-Dapp > 2.8 nM), The 1,3-propanediol (Pr) residue-containing DNA seems to be the minimal AP site structure allowing a Fpg specific DNA binding, since the ethyleneglycol residue is not specifically bound by these enzymes.

The binding of Escherichia coli and Lactococcus lactis Fapy-DNA glyosylase (Fpg) proteins to DNA containing either cyclic or non-cyclic abasic (AP) site analogs was investigated by electrophoretic mobility shift assay (EMSA) and by footprinting experiments. We showed that the reduced AP site is the best substrate analog for the E. coli and L. lactis enzymes (K-Dapp = 0.26 and 0.5 nM, respectively) as compared with the other analogs tested in this study (K-Dapp > 2.8 nM), The 1,3-propanediol (Pr) residue-containing DNA seems to be the minimal AP site structure allowing a Fpg specific DNA binding, since the ethyleneglycol residue is not specifically bound by these enzymes.

Thomas, M ; Castaing, B ; Fourrey, JL ; Zelwer, C  (1999)

Synthesis of an enantiomerically pure carbocyclic DNA abasic site analogue

Nucleosides Nucleotides & Nucleic Acids 18 (2) 239-243
A short synthetic route to an appropriately derivatized carbocyclic analogue of abasic site residues of DNA is proposed.

A short synthetic route to an appropriately derivatized carbocyclic analogue of abasic site residues of DNA is proposed.

Coste, F ; Hervouet, N ; Oberto, J ; Zelwer, C ; Castaing, B  (1999)

Crystallization and preliminary X-ray diffraction analysis of the homodimeric form a(2) of the HU protein from Escherichia coli

Acta Crystallographica Section D-Biological Crystallography 55 1952-1954 Part 11
The homodimeric form a(2) of the Escherichia coli DNA-binding protein HU was crystallized by the hanging-drop vapour-diffusion method using PEG 4000 as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 31.09, b = 55.34, c = 117.63 Angstrom, and contain one monomer per asymmetric unit. A full diffraction data set was collected to 2.3 Angstrom resolution on a conventional X-ray source. The molecular-replacement method, using the HU crystallographic model from Bacillus stearothermophilus as a starting point, gave a reliable solution for the rotation and translation functions.

The homodimeric form a(2) of the Escherichia coli DNA-binding protein HU was crystallized by the hanging-drop vapour-diffusion method using PEG 4000 as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 31.09, b = 55.34, c = 117.63 Angstrom, and contain one monomer per asymmetric unit. A full diffraction data set was collected to 2.3 Angstrom resolution on a conventional X-ray source. The molecular-replacement method, using the HU crystallographic model from Bacillus stearothermophilus as a starting point, gave a reliable solution for the rotation and translation functions.


1995   Références trouvées : 1

Castaing, B ; Zelwer, C ; Laval, J ; Boiteux, S  (1995)

HU protein of escherichia-coli binds specifically to DNA that contains single-strand breaks or gaps

Journal of Biological Chemistry 270 (17) 10291-10296
In this study, we have identified a protein in Escherichia coli that specifically binds to double-stranded DNA containing a single-stranded gap of one nucleotide. The gap-DNA binding (GDB) protein was purified to apparent homogeneity, The analysis of the amino-terminal sequencing of the GDB protein shows two closely related sequences we identify as the a and ß subunits of the HU protein, Furthermore, the GDB protein is not detected in the crude extract of an E. coli double mutant strain hupA hupB that has no functional HU protein.

In this study, we have identified a protein in Escherichia coli that specifically binds to double-stranded DNA containing a single-stranded gap of one nucleotide. The gap-DNA binding (GDB) protein was purified to apparent homogeneity, The analysis of the amino-terminal sequencing of the GDB protein shows two closely related sequences we identify as the a and ß subunits of the HU protein, Furthermore, the GDB protein is not detected in the crude extract of an E. coli double mutant strain hupA hupB that has no functional HU protein.


1993   Références trouvées : 2

Oconnor, TR ; Graves, RJ ; Demurcia, G ; Castaing, B ; Laval, J  (1993)

FPG protein of escherichia-coli is a zinc finger protein whose cysteine residues have a structural and or functional-role

Journal of Biological Chemistry 268 (12) 9063-9070
The Fpg protein of Escherichia coli is a DNA repair enzyme with DNA glycosylase, abasic site nicking, and deoxyribose excising activities. Analysis of the amino acid sequence of this protein suggests that the Fpg protein is a zinc finger protein with a Cys-X2-Cys-X16-Cys-X2-Cys motif. Competition experiments show that the Fpg protein substitutes Cu(II), Cd(II), and Hg(II), metal ions classically associated with substitutions in zinc finger proteins. The Fpg protein activities are inhibited following the reaction with a Cys-specific reagent at low protein:reagent ratios, suggesting that these residues are important for the enzymatic activities. Site-directed mutagenesis was used to produce 6 mutant Fpg proteins with Cys —> Gly mutations.

The Fpg protein of Escherichia coli is a DNA repair enzyme with DNA glycosylase, abasic site nicking, and deoxyribose excising activities. Analysis of the amino acid sequence of this protein suggests that the Fpg protein is a zinc finger protein with a Cys-X2-Cys-X16-Cys-X2-Cys motif. Competition experiments show that the Fpg protein substitutes Cu(II), Cd(II), and Hg(II), metal ions classically associated with substitutions in zinc finger proteins. The Fpg protein activities are inhibited following the reaction with a Cys-specific reagent at low protein:reagent ratios, suggesting that these residues are important for the enzymatic activities. Site-directed mutagenesis was used to produce 6 mutant Fpg proteins with Cys —> Gly mutations.

Castaing, B ; Geiger, A ; Seliger, H ; Nehls, P ; Laval, J ; Zelwer, C ; Boiteux, S  (1993)

Cleavage and binding of a DNA fragment containing a single 8-oxoguanine by wild-type and mutant fpg proteins

Nucleic Acids Research 21 (12) 2899-2905
A 34-mer oligonucleotide containing a single 7,8-dihydro-8-oxoguanine (8-OxoG) residue was used to study the enzymatic and DNA binding properties of the Fpg protein from E.coli. The highest rates of incision of the 8-OxoG containing strand by the Fpg protein were observed for duplexes where 8-OxoG was opposite C (*G/C) or T (*G/T). In contrast, the rates of incision of duplexes containing 8-OxoG opposite G (*G/G) and A (*G/A) were 5-fold and 200-fold slower. Gel retardation studies showed that the Fpg protein had a strong affinity for duplexes where the 8-OxoG was opposite pyrimidines and less affinity for duplexes where the 8-OxoG was opposite purines. K(D)app values were 0.6 nM (*G/C), 1.0 nM (*G/T), 6.0 nM (*G/G) and 16.0 nM (*G/A).

A 34-mer oligonucleotide containing a single 7,8-dihydro-8-oxoguanine (8-OxoG) residue was used to study the enzymatic and DNA binding properties of the Fpg protein from E.coli. The highest rates of incision of the 8-OxoG containing strand by the Fpg protein were observed for duplexes where 8-OxoG was opposite C (*G/C) or T (*G/T). In contrast, the rates of incision of duplexes containing 8-OxoG opposite G (*G/G) and A (*G/A) were 5-fold and 200-fold slower. Gel retardation studies showed that the Fpg protein had a strong affinity for duplexes where the 8-OxoG was opposite pyrimidines and less affinity for duplexes where the 8-OxoG was opposite purines. K(D)app values were 0.6 nM (*G/C), 1.0 nM (*G/T), 6.0 nM (*G/G) and 16.0 nM (*G/A).


1992   Références trouvées : 1

Castaing, B ; Boiteux, S ; Zelwer, C  (1992)

DNA containing a chemically reduced apurinic site is a high-affinity ligand for the escherichia-coli formamidopyrimidine-DNA glycosylase

Nucleic Acids Research 20 (3) 389-394
The E. coli Formamidopyrimidine-DNA Glycosylase (FPG protein), a monomeric DNA repair enzyme of 30.2 kDa, was purified to homogeneity in large quantities. The FPG protein excises imidazole ring-opened purines and 8-hydroxyguanine residues from DNA. Besides DNA glycosylase activity, the FPG protein is endowed with an EDTA-resistant activity which nicks DNA at apurinic/apyrimidic sites (AP sites). In contrast, DNAs containing chemically reduced AP sites are not incised by the FPG protein. However, the DNA glycosylase activity of the FPG protein is strongly inhibited in the presence of a purified synthetic 24 base-pair double-stranded oligonucleotide which contains a single apurinic site transformed chemically through borohydride reduction into a ring-opened deoxyribose derivative.

The E. coli Formamidopyrimidine-DNA Glycosylase (FPG protein), a monomeric DNA repair enzyme of 30.2 kDa, was purified to homogeneity in large quantities. The FPG protein excises imidazole ring-opened purines and 8-hydroxyguanine residues from DNA. Besides DNA glycosylase activity, the FPG protein is endowed with an EDTA-resistant activity which nicks DNA at apurinic/apyrimidic sites (AP sites). In contrast, DNAs containing chemically reduced AP sites are not incised by the FPG protein. However, the DNA glycosylase activity of the FPG protein is strongly inhibited in the presence of a purified synthetic 24 base-pair double-stranded oligonucleotide which contains a single apurinic site transformed chemically through borohydride reduction into a ring-opened deoxyribose derivative.


1991   Références trouvées : 1

Zagorski, W ; Castaing, B ; Herbert, CJ ; Labouesse, M ; Martin, R ; Slonimski, PP  (1991)

Purification and characterization of the saccharomyces-cerevisiae mitochondrial leucyl transfer-rna synthetase

Journal of Biological Chemistry 266 (4) 2537-2541
We have purified the product of the NAM2 gene, the mitochondrial leucyl-tRNA synthetase, from yeast mitochondria. The purified protein cross-reacts with antibodies raised against the product of a LacZ/NAM2 gene fusion and antibodies raised against the purified Escherichia coli leucyl-tRNA synthetase. The mass as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is about 100 kDa, consistent with the size predicted by the gene sequence (102 kDa). The N-terminal sequence of the protein has been determined and shows that the first nine amino acids predicted by the gene sequence have been removed, probably during transport into the mitochondria.

We have purified the product of the NAM2 gene, the mitochondrial leucyl-tRNA synthetase, from yeast mitochondria. The purified protein cross-reacts with antibodies raised against the product of a LacZ/NAM2 gene fusion and antibodies raised against the purified Escherichia coli leucyl-tRNA synthetase. The mass as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is about 100 kDa, consistent with the size predicted by the gene sequence (102 kDa). The N-terminal sequence of the protein has been determined and shows that the first nine amino acids predicted by the gene sequence have been removed, probably during transport into the mitochondria.


1984   Références trouvées : 1

Castaing, B  (1984)

The growth resistance of HE-4 solid superfluid interfaces

Journal de Physique : Lettres 45 (5) L233-L239


Mots-clés

Directeur de recherche , Responsable de groupe thématique , Biologie de l’ARN et ARN thérapeutiques