The hexameric helicase DnaB unwinds the DNA duplex at the Escherichia coli chromosome replication fork. 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. This N-terminal domain is required both for interaction with other proteins in the primosome and for DnaB helicase activity [1].

1: Crystal structure of the N-terminal domain of the DnaB hexameric helicase. Fass D, Bogden CE, Berger JM; Structure Fold Des 1999;7:691-698. PMID:10404598