Primase Directs the Release of DnaC from DnaB

SummaryAn AAA+ ATPase, DnaC, delivers DnaB helicase at the E. coli chromosomal origin by a poorly understood process. This report shows that mutant proteins bearing alanine substitutions for two conserved arginines in a motif named box VII are defective in DNA replication, but this deficiency does not arise from impaired interactions with ATP, DnaB, or single-stranded DNA. Despite their ability to deliver DnaB to the chromosomal origin to form the prepriming complex, this intermediate is inactive. Quantitative analysis of the prepriming complex suggests that the DnaB-DnaC complex contains three DnaC monomers per DnaB hexamer and that the interaction of primase with DnaB and primer formation triggers the release of DnaC, but not the mutants, from DnaB. The interaction of primase with DnaB and the release of DnaC mark discrete events in the transition from initiation to the elongation stage of DNA replication.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (334 K)Download as PowerPoint slideHighlights► At oriC, primase interacts with DnaC to dissociate DnaC from the DnaB-DnaC complex ► The DnaB-DnaC complex at oriC contains three DnaC monomers per DnaB hexamer ► After DnaC dissociates, DnaB helicase can move to open the replication fork