Interaction of dnaA46 protein with a stimulatory protein in replication from the Escherichia coli chromosomal origin

Highly purified preparations of dnaA46 protein have permitted its biochemical characterization in comparison with the activities of wild type dnaA protein. We have determined that dnaA46 protein was reduced in its ability to bind to DNA fragments containing oriC. This mutant protein was also defective in binding ATP and was inactive for replication of oriC-containing plasmids in purified enzyme systems. In contrast, dnaA46 protein was active for oriC plasmid replication when added to reactions containing a crude enzyme fraction deficient in dnaA protein. One or more proteins have been identified which appear to interact with dnaA46 protein prior to DNA synthesis. These studies suggest that this interaction is thermolabile. Stimulation of dnaA46 protein activity resulted in a reduction of the prolonged lag prior to DNA synthesis.