TOPOLOGY OF THE MITOCHONDRIAL CAMP-DEPENDENT PROTEIN-KINASE AND ITS SUBSTRATES

In intact bovine heart mitochondria, cAMP-dependent phosphorylation of 42, 29, 18 and 6.5 kDa proteins was inhibited by carboxyatractyloside . This shows that both mitochondrial cAMP-dependent protein kinase (mt PKA) and its protein substrates are localized at the matrix side of th e inner mitochondrial membrane, Proteins of 42, 29, 18, and 6.5 kDa we re also bound at the outer surface of mitochondria where they were pho sphorylated by the added purified catalytic subunit of PKA. In the cyt osol from bovine heart proteins of the above molecular weights were ph osphorylated by the cytosolic PKA.