INFLUENCE OF CLUSTER FORMATION OF ACIDIC PHOSPHOLIPIDS ON DECREASE INTHE AFFINITY FOR ATP OF DNAA PROTEIN

DnaA protein is the initiator of chromosomal DNA replication in Escher ichia coli. We examined the influence of artificial mixed membrane com posed of synthetic acidic (phosphate) lipid and basic (ammonium) lipid on the affinity of DnaA protein for ATP. Two sets of acidic and basic lipids with distinguishable numbers of hydrophobic alkyl chains were devised. Synthetic membranes made of the sole acidic Lipid but not the basic bilayers inhibited the ATP binding to DnaA protein and stimulat ed the release of ATP from the ATP-DnaA complex. The basic bilayer-for ming compounds served as the matrix for the guest acidic lipids. Acidi c lipids dispersed in the basic matrix membrane had little effect on A TP binding and on ATP release. Conversely, acidic lipids forming clust er structures in the mixed artificial membranes inhibited the ATP bind ing and stimulated the release of ATP. These observations suggest that in mixed lipid bilayers, a cluster structure of acidic lipids seems t o be an important parameter to decrease the affinity of DnaA protein f or ATP.