Practice question

DnaB helicase requires accessory factor DnaC, an AAA+ ATPase chaperone, to load onto oriC melted bubble during initiation step. DnaC binds DnaB hexamer hexamer in inactive ATP-bound state, inhibits its ATPase and helicase to prevent premature unwinding outside origin, and actively delivers complex to DnaA-origin complex at DUE. Upon ATP hydrolysis by DnaC, DnaC releases ADP form and DnaB becomes active to expand replication bubble bidirectionally. Loader mechanism parallels eukaryotic Cdc6-MCM loading and ensures helicase placed specifically at origin onto each separated strand opposite orientation.