Although the mechanism by which DnaB both couples ATP hydrolysis to translocation along DNA and denatures the duplex is unknown, a change in the quaternary structure of the protein involving dimerisation of the N-terminal domain has been observed and may occur during the enzymatic cycle.
Mechanical energy moves the DnaB into the replication fork, physically splitting it in half.
In E. coli, dnaB is a hexameric protein of six 471-residue subunits, which form a ring-shaped structure with threefold symmetry.
Eight DnaA protein molecules, all in the ATP-bound state, assemble to form a helical complex encompassing the R and I sites in oriC.
The complex formed at the replication origin also includes several DNA-binding proteins- Hu, IHF and FIS that facilitate DNA bending.
A hexamer of DnaC, each subunit bound to ATP, forms a tight complex with the hexameric, ring-shaped DnaB helicase.
The DnaB helicases loaded onto the two DNA strands thus travel in opposite directions, creating two potential replication forks.