Further study on the magnesium-mediated change in physical state of phospholipid modulates mitochondrial F0-F1-ATPase activity.

We have postulated that magnesium may play a role in altering the lipid fluidity of the bilayers, which would induce a change of conformation of the F0-ATPase portion (buried in the lipid core) of mitochondrial F0-F1-ATPase. Such change could be transmitted to the soluble F1 portion, resulting in higher enzymatic activity. The assumption was further supported by the results presented in the following: (1) A conformational difference for the F0-ATPase-containing proteoliposomes induced by the magnesium effect could be detected using a fluorescent probe acrylodan; (2) H(+)-translocation activity of F0-ATPase-incorporated proteoliposomes with magnesium, monitoring by fluorescence quenching of 9-aminoacridine or the bulk phase pH change, was higher than that without magnesium; (3) The magnesium effect on the reconstituted F0-F1-ATPase activity was greatly enhanced when the reconstitution was carried out in the presence of oligomycin sensitivity conferring protein (OSCP, a main component of the connecting link between the F1 and F0 sector of F0-F1-ATPase).