cAMP-dependent protein kinase and phosphoproteins in mammalian mitochondria. An extension of the cAMP-mediated intracellular signal transduction

Evidence has been obtained for the occurrence of a cAMP-dependent serine pr otein kinase associated with the inner membrane/matrix of mammalian mitocho ndria. The catalytic site of this kinase is localized at the inner side of the inner membrane, where it phosphorylates a number of mitochondrial prote ins. One of these has been identified as the AQDQ subunit of complex I, cAM P-dependent phosphorylation of this protein promotes the activity of comple x I and mitochondrial respiration. A 5 bp duplication in the nuclear gene e ncoding this protein has been found in a human patient, which eliminates th e phosphorylation site. PKA anchoring proteins have recently been identifie d in the outer membrane of mammalian mitochondria, which could direct phosp horylation of proteins at contact sites with other cell structures. (C) 199 9 Federation of European Biochemical Societies.