Rapid Labeling of Mitochondrial Lipids by Labeled Orthophosphate and Adenosine Triphosphate

Abstract

Abstract Rapidly labeled lipids of guinea pig liver mitochondria incubated with 32Pi or γ-32P-ATP were studied. With the use of inhibitors of oxidative phosphorylation, it was shown that 32Pi is converted to labeled ATP, which is the more direct precursor of labeled lipid. Atractyloside blocks phosphorylation of lipid by endogenous ATP under conditions in which it has little effect on oxidative phosphorylation or lipid labeling by externally added ATP. Two radioactive lipids were identified by chromatography as phosphatidylinositol phosphate and phosphatidic acid. The properties of an unknown third lipid were studied. Its formation was selectively blocked by the addition of hydroxylamine to the incubation medium. It is postulated that the lipids are labeled by the action of kinases and phosphatases in the mitochondrial fraction.