DnaB helicase

DnaB helicase is an enzyme in prokaryotes which opens the replication fork during DNA replication. Initially when DnaB binds to dnaA, it is associated with dnaC, a negative regulator. After dnaC dissociates, dnaB binds dnaG.

In eukaryotes, helicase function is provided by the T antigen.

The DnaB helicase is the product of the dnaB gene. The helicase enzyme that is produced is a hexamer in E. coli, as well as in many other prokaryotes. The energy for DnaB activity is provided by NTP hydrolysis, which in fact is translated into mechanical energy which then moves the DnaB into the replication fork, physical splitting it in half

E.coli DnaB
In E. coli DnaB is a hexameric protein of six 471 residue subunits. It is bound to the lagging strand, and can hydrolyse all NTPs except UTP. It is a ring structure which allows a DNA strand to flow through the middle. In this way, the binding of NTPs causes a conformation change the makes the DnaB move and mechanically separate the two strands