ROLE OF ADENINE-NUCLEOTIDES, MOLECULAR CHAPERONES AND CHAPERONINS IN STABILIZATION OF DNAA INITIATOR PROTEIN OF ESCHERICHIA-COLI

DnaA protein of Escherichia coli is a sequence-specific DNA binding pr otein required for the initiation of DNA replication from the chromoso mal origin, oriC, and of several E. coli plasmids. At a moderate ionic strength, purified DnaA protein has a strong tendency to aggregate; t he self-aggregate form is inactive in DNA replication. Binding of ATP or ADP to DnaA protein protected it from aggregation to maintain its r eplication activity. AMP or cyclic AMP had no protective effect. The m olecular chaperone DnaK protected DnaA protein from aggregation with o r without ATP. DnaJ and GrpE were not stimulatory. Chaperonins GroEL a nd GroES were also able to prevent aggregation but only in the presenc e of ATP. The studies presented here show that for DnaA protein to be active in the initiation of DNA replication, it must be prevented from forming a self-aggregate by the binding of adenine nucleotides, and/o r by the action of molecular chaperones. (C) 1998 Elsevier Science B.V . All rights reserved.