THE INITIATOR FUNCTION OF DNAA PROTEIN IS NEGATIVELY REGULATED BY THESLIDING CLAMP OF THE ESCHERICHIA-COLI CHROMOSOMAL REPLICASE

The beta subunit of DNA polymerase III is essential far negative regul ation of the initiator protein, DnaA. DnaA inactivation occurs through accelerated hydrolysis of ATP bound to DnaA; the resulting ADP-DnaA f ails to initiate replication. The ability of beta subunit to promote D naA inactivation depends on its assembly as a sliding clamp on DNA and must be accompanied by a partially purified factor, IdaB protein. Dna A inactivation in the presence of IdaB and DNA polymerase III is furth er stimulated by DNA synthesis, indicating close linkage between initi ator inactivation and replication. In vivo, DnaA predominantly takes o n the ADP form in a beta 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.