DnaB helicase is an enzyme in bacteria which opens the replication fork during DNA replication. 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. Initially when DnaB binds to dnaA, it is associated with dnaC, a negative regulator. After DnaC dissociates, DnaB binds dnaG.
The N-terminal has a multi-helical structure that forms an orthogonal bundle. The C-terminal domain contains an ATP-binding site and is therefore probably the site of ATP hydrolysis.
In eukaryotes, helicase function is provided by the MCM (Minichromosome maintenance) complex.
The DnaB helicase is the product of the dnaB gene. DnaB is expressed as a monomer and oligomerises into hexamer through N-terminal interactions. Replicative helicases have a central ring and that feature is conserved across bacterial to eukaryotes.
The energy for DnaB activity is provided by NTP hydrolysis. Mechanical energy moves the DnaB into the replication fork, physically splitting it in half.