Protein--protein interactions in the eubacterial replisome

Replication of genomic DNA is a universal process that proceeds in distinct stages, from initiation to elongation and finally to termination. Each stage involves multiple stable or transient interactions between protein subunits with functions that are more or less conserved in all organisms. In Escherichia coli, initiation of bidirectional replication at the origin (oriC) occurs through the concerted actions of the DnaA replication initiator protein, the hexameric DnaB helicase, the DnaC?helicase loading partner and the DnaG primase, leading to establishment of two replication forks. Elongation of RNA primers at each fork proceeds simultaneously on both strands by actions of the multimeric replicase, DNA polymerase III holoenzyme. The fork that arrives first in the terminus region is halted by its encounter with a correctly-oriented complex of the Tus replication terminator protein bound at one of several Ter sites, where it is trapped until the other fork arrives. We summarize current understanding of interactions among the various proteins that act in the different stages of replication of the chromosome of E. coli, and make some comparisons with the analogous proteins in Bacillus subtilis and the coliphages T4 and T7.