dnaC

DnaC is a bacterial DNA replication initiation factor that functions as a helicase loader for the DnaB helicase. In Escherichia coli and many related bacteria, DnaC binds to the DnaB helicase and delivers it to the origin of replication (oriC) during the initiation of DNA synthesis. The DnaB helicase then unwinds the parental DNA duplex, allowing the replication machinery to assemble and begin synthesis. RNA primers are subsequently laid down by the primase DnaG.

DnaC is an ATPase of the AAA+ family. It binds ATP to form a complex with DnaB and interacts with oriC-bound DnaA, which promotes origin melting and the loading of DnaB onto single-stranded DNA. After DnaB is properly loaded, ATP hydrolysis by DnaC triggers the dissociation of DnaC from DnaB, enabling DnaB helicase activity to proceed and unwind DNA during replication. DnaC itself is not a permanent part of the elongating replisome; it is recycled after the loading step.

Genetic and biochemical studies indicate that dnaC is essential for initiation in E. coli. Its activity is coordinated with the cell cycle and the nucleotide-bound state of DnaC, as well as the origin-binding status of DnaA. Homologs or functionally analogous helicase loaders exist in other bacteria, reflecting diversity in replication initiation systems across species. DnaC interacts with key initiation factors, including DnaA, DnaB, and DnaG, as part of the initiation cascade.

See also: DnaA, DnaB, DnaG.