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Typologie d'actualités: Group Synthetic protein and Bioorthogonal Chemistry
New methodological breakthrough in total protein synthesis
Since the first synthesis of an amino acid dimer in the late 19th century, synthetic proteins represented a fascinating goal for generations of chemists. Invented in the 1960s, the solid phase peptide synthesis (SPPS) technology is since used routinely for peptides made up of a few dozen amino acids. The discovery of "chemical ligation" reactions in the 1990s paved the way to the synthesis of proteins of more than one hundred amino acids: extremely selective chemical reactions are used under aqueous conditions to couple peptide segments - themselves synthesized by SPPS -, devoted of side chain protective groups usually required in organic synthesis. Thanks to these methodological breackthroughs, the chemical approach to protein synthesis today advantageously complements biotechnological methods and enable the generation of native or modified proteins, tailor-made tools for deciphering biological processes at atomic resolution.
However, the synthesis of proteins of several hundred amino acids requires numerous successive chemical ligations, and therefore particularly delicate stages of purification of the reaction intermediates. One solution to overcome these steps is to assemble the proteins onto a solid support. Although very attractive, this approach has been limited to proofs of concept: one of the main reasons is the difficulty of grafting on a suitable solid support the first peptide segment through a linker that can be easily cleaved once the ligations carried out. Indeed, the conditions required for cleaving the linkers developed so far are incompatible with many proteins.
To overcome this problem, CBM scientists, in collaboration with colleagues from IC2MP in Poitiers, explored linkers programmed to be cleaved under very mild conditions by an enzymatic reaction. Remarkably, the size of the enzyme directly correlates with the rate at which the arm is cleaved, and therefore with the efficiency of the release of the synthesized protein. The method was applied to the synthesis of a peptide of 160 amino acids, which is to date the longest sequence ever synthesized by solid phase chemical ligations.
Reference of the article : S. A. Abboud, M. Amoura, J.-B. Madinier, B. Renoux, S. Papot, V. Piller, V. Aucagne. Enzyme-cleavable linkers for protein chemical synthesis through solid-phase ligations, Angew. Chem. Int. Ed., 2021, accepted article. https://doi.org/10.1002/anie.202103768
See the news on the website of the CNRS institute of chemistry
Biotechnocentre 33rd conference
The 33rd Biotechnocentre conference will be held on October 7 and 8, 2021 at Center Parcs Domaine Les Hauts de Bruyères - Rue Lamotte - 41 600 Chaumont-sur-Tharonne.
With the participation of Doctoral School 549 "Santé, Sciences Biologiques et Chimie du Vivant" (SSBCV).
Among the speakers announced, Vincent Aucagne, head of the thematic group "Synthetic proteins and bioorthogonal chemistry" " will give a conference entitled "Methodological developments for the chemical synthesis of proteins"
Registration before September 3, 2021 at biotechnocentre@sfr.fr
January 31st, 2020 : External seminar Gosuke Hayashi, Nagoya university, Japan
Antimicrobial peptides: an atypical double-domain avian defensin, specifically found in eggs, reveals multiple roles in protection of the embryo
Gga-AvBD11, the avian β-defensin 11 of the common chicken Gallus gallus (Gga-AvBD11), is egg-specific, and represents the sole double-sized defensin (9.3 kDa) among the 14 AvBDs reported in the chicken species. The appearance of such a double-domain protein during evolution could be driven either by its increased biological potency compared to a single domain molecule, and/or by the necessity to acquire new functions carried only by the full-length protein. To assess the contribution of the two domains, we chemically synthesized them. We determined the 3D NMR structure each domain, and the structure of the compact full-length Gga-AvBD11, composed of two packed β-defensin domains. There is no reference for such a double-β-defensin in structural databanks. Thus, AvBD11 is the archetype of a new structural family, which we named avian-double-β-defensins (Av-DBD).
Its high sequence conservation among birds suggests its essential roles in the avian egg. In collaboration with several teams (Nouzilly and Tours, France), we showed that Gga-AvBD11 displays antimicrobial activities against Gram+ and Gram- bacterial pathogens, the avian protozoan Eimeria tenella and avian influenza virus (H1N1). It also shows cytotoxic and anti-invasive activities, suggesting that it may be involved in the (re-)modeling of embryonic tissues. Our results point to a critical importance of the cationic N-ter domain in mediating antibacterial, antiparasitic and anti-invasive activities, with the C-ter domain potentiating the two latter activities. Strikingly, antiviral activity in infected chicken cells requires the full-length protein.
The benefit for the avian species of possessing a double-sized defensin is a fascinating question. In order to better understand the structure-activity and phylogenetic relationships of AvBD11s family, we are currently studying other AvBD11 proteins (SAPhyR-11 project grant from the Région Centre Val de Loire).
This work was funded by the MUSE (Grant no. 2014-00094512) and SAPhyR-11 (Grant no. 2017-119983) project grants from the Région Centre-Val de Loire.
Structure, function, and evolution of Gga-AvBD11, the archetype of the structural avian-double-β-defensin family
Nicolas Guyot, Hervé Meudal, Sascha Trapp, Sophie Iochmann, Anne Silvestre, Guillaume Jousset, Valérie Labas, Pascale Reverdiau, Karine Loth, Virginie Hervé, Vincent Aucagne, Agnès F. Delmas, Sophie Rehault-Godbert, and Céline Landon
PNAS January 7, 2020 117 (1) 337-345; first published December 23, 2019 https://doi.org/10.1073/pnas.1912941117
Antimicrobial peptides: How peptide chemistry and NMR shed light on the antimicrobial activity of big defensins
Big defensins, ancestors of β-defensins, are composed of a β-defensin-like C-terminal domain and a hydrophobic ancestral N-terminal domain.
This unique structure is found in a limited number of phylogenetically distant species, mostly living in marine environments. Using solid phase peptide chemistry and native chemical ligation, we produced the oyster Crassostrea gigas BigDef1 (Cg-BigDef1) and its separate domains and characterized their 3D structure by NMR. Cg-BigDef1 showed salt-stable and broad-range bactericidal activity, including against multidrug-resistant clinical isolates of S. aureus. We found that the ancestral N-terminal domain confers salt-stable antimicrobial activity to the β-defensin-like domain, which is otherwise inactive. Moreover, upon contact with bacteria, the N-terminal domain drives Cg-BigDef1 assembly into nanonets that entrap and kill bacteria. We speculate that the hydrophobic N-terminal domain of big defensins has been retained in marine phyla to confer salt-stable interactions with bacterial membranes in environments where electrostatic interactions are impaired.
Those remarkable properties open the way to future drug developments when physiological salt concentrations inhibit the antimicrobial activity of vertebrate β-defensins (ANR MOSAR-Def 2019-2023).
Many thanks to D. Destoumieux-Garzón for collaboration, to “Vaincre La Mucovidose“ and CNRS PEPS X-life” for funding.
21st Congress of the French Group of Peptides and Proteins (GFPP)
The next meeting of the French peptide and protein group will take place in Amboise (Villa Bellagio), from Sunday 12 to Thursday 16 May 2019, in the beautiful and historic Loire Valley.
It should be noted that 2019 will mark the 41st anniversary of the creation of the GFPP and also the 500th anniversary of the death of Leonardo da Vinci, who spent his last years in Amboise, at the Château du Clos-Lucé, located a few kilometers from the center conferences.
The conference program covers cutting-edge topics in the field of peptides and proteins.