Plasmid replication initiator RepB forms a hexamer reminiscent of ring helicases and has mobile nuclease domains.

ABSTRACT: RepB initiates plasmid rolling-circle replication by binding to a triple 11-bp direct repeat (bind locus) and cleaving the DNA at a specific distant site located in a hairpin loop within the nic locus of the origin. The structure of native full-length RepB reveals a hexameric ring molecule, where each protomer has two domains. The origin-binding and catalytic domains show a three-layer alpha-beta-alpha sandwich fold. The active site is positioned at one of the faces of the beta-sheet and coordinates a Mn2+ ion at short distance from the essential nucleophilic Y99. The oligomerization domains (ODs), each consisting of four alpha-helices, together define a compact ring with a central channel, a feature found in ring helicases. The toroidal arrangement of RepB suggests that, similar to ring h

SUBMITTER: Boer DR 

PROVIDER: S-EPMC2693155 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature