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Accueil > Publications > Recherche par années > Années 2000 > 2006

Walmacq, C ; Rahmouni, AR ; Boudvillain, M

Testing the steric exclusion model for hexameric helicases : Substrate features that alter RNA-DNA unwinding by the transcription termination factor Rho

Biochemistry 45 (18) 5885-5895

par Administrateur - publié le

Abstract :

Typical hexameric helicases form ring-shaped structures involved in DNA replication. These enzymes have been proposed to melt forked DNA substrates by binding to, and pulling, one strand within their central channel, while the other strand is forced outside of the hexamer by steric exclusion and specific contacts with the outer ring surface. Transcription termination factor Rho also assembles into ring-shaped hexamers that are capable to use NTP-derived energy to unwind RNA and RNA-DNA helices. To delineate the potential relationship between helicase structural organization and unwinding mechanism, we have performed in vitro Rho helicase experiments with model substrates containing an RNA-DNA helix downstream from a Rho loading site. We show that a physical discontinuity (nick) inhibits RNA-DNA unwinding when present in the RNA but not in the DNA strand.