The β subunit of DNA polymerase III is essential for negative regulation of the initiator protein, DnaA. DnaA inactivation occurs through accelerated hydrolysis of ATP bound to DnaA; the resulting ADP-DnaA fails to initiate replication. The ability of β subunit to promote DnaA inactivation depends on its assembly as a sliding clamp on DNA and must be accompanied by a partially purified factor, IdaB protein. DnaA inactivation in the presence of IdaB and DNA polymerase III is further stimulated by DNA synthesis, indicating close linkage between initiator inactivation and replication. In vivo, DnaA predominantly takes on the ADP form in a β subunit-dependent manner. Thus, the initiator is negatively regulated by action of the replicase, a mechanism that may be key to effective control of the replication cycle.
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)