Phospholipids promote dissociation of ADP from the Mycobacterium avium DnaA protein

The biochemical aspects of the initiation of DNA replication in Mycobacterium avium are unknown. As a first step towards understanding this process, M. avium DnaA protein, the counterpart of Escherichia coli replication initiator protein, was overproduced in E. coli with an N-terminal histidine tag and purified to homogeneity on a nickel affinity column. The recombinant DnaA protein bound both ATP and ADP with high affinity and showed a weak ATPase activity. ADP, following the hydrolysis of ATP, remained bound to the protein strongly and the exchange of ATP for bound ADP was found to be weak. Acidic phopsholipids such as phosphatidylinositol, phosphatidylglycerol, and cardiolipin, promoted the dissociation of ADP from the DnaA protein, whereas the neutral phospholipid, phosphatidylethanolamine, did not. The phospholipid promoted dissociation of ADP from DnaA protein was stimulated in the presence of the M. avium origin of replication. We suggest that the initiation of DNA replication in M. avium involves an interplay among DnaA, adenine nucleotides and phospholipids.