Diphosphatidylglycerol-induced changes in the organization of mitochondrial ATPase

1. On submitochondrial particles from bovine heart, diphosphatidylglycerol produced a selective solubilization of ATPase. The solubilized enzyme was purified further by ammonium sulfate fractionation and shown to have the same reconstitutive activity as coupling factor F₁ (Pullman, M.E., Penefsky, H. S., Datta, A. and Racker, E. (1960) J. Biol. Chem. 235, 3322–3329).

2. Diphosphatidylglycerol-treated submitochondrial particles retained large amounts of the phospholipid and showed a decreased ATPase activity. Once the excess of phospholipid was removed, soluble ATPase could be again reincorporated in an oligomycin-sensitive complex.

3. On Mg-ATP particles the solubilization of ATPase induced by diphosphatidylglycerol was preceded by a stimulation of oligomycin-sensitive ATPase which indicated a dissociation of F₁ from the ATPase inhibitor (Pullman, M. E. and Monroy, G. C. (1963) J. Biol. Chem. 238, 3762–3769). Magnesium was required to obtain the oligomycin-sensitive stimulation whereas in the absence of magnesium the solubilization of ATPase was prevalent.

4. It is concluded that the decreased association of F₁ with the ATPase inhibitor produced by diphosphatidylglycerol, causes a labilization of ATPase-membrane interaction. Under particular conditions, e.g. a high amount of phospholipid and a low concentration of magnesium, this is followed by the detachment of ATPase.