Protein phosphorylation in isolated mitochondria and the effects of protein kinase C.

When isolated intact rat liver mitochondria are incubated with [gamma-32P]ATP the major phosphorylated proteins are those of 47 and 36 kDa. Phosphorylation of the 47 kDa protein, but not of the 36 kDa protein, is inhibited by carboxyatractyloside, an inhibitor of mitochondrial ATP uptake, while phosphorylation of the 36 kDa protein is inhibited by various uncouplers and an inhibitor of mitochondrial respiration. Addition of purified protein kinase C to the isolated mitochondria leads to the phosphorylation of 69, 37 and 17 kDa proteins. As with other substrates for protein kinase C, phosphorylation of these proteins is dependent on Ca2+ and markedly stimulated by various tumor promoters.