Labeling of mitochondrial phosphatidyl inositol phosphate by Pi32 and by [gamma]P32ATP

Abstract

Garbus et al., 1963 reported labeling of mitochondrial phospholipid following short incubations with Pi32. The rapidly labeled lipid has been identified by means of alkaline hydrolysis as phosphatidyl inositol phosphate (Garbus et al., 1963; Gaillard and Hawthorne, 1963; Morgan, 1964). Inhibitors of oxidative phosphorylation blocked incorporation of Pi32 into lipid, although the reported effects of oligomycin were variable (Garbus et al., 1963; Michell et al., 1964). While such studies suggest that a high energy intermediate is required for the phosphorylation of phosphatidyl inositol, no evidence for its nature has been presented. This communication shows that the fraction of radioactivity in [gamma]P32ATP incorporated into lipid is greater than that incorporated from Pi32 and further that inhibitors of oxidative phosphorylation, particularly atractyloside, can inhibit the labeling of lipid from Pi32 but have no effect on labeling from [gamma]P32ATP.