Identification and primary structure of the cardiolipin-binding domain of mitochondrial creatine kinase

It was recently shown that the mitochondrial isozyme of heart creatine kinase binds to cardiolipin on the outer half of the inner membrane [Müller, M., et al. (1985) J. Biol. Chem. 260, 3839-3843]. The enzyme has now been extracted and purified to homogeneity from rat heart mitochondria, and cleaved with CNBr. The fragments have been separated on an FPLC system using a Mono Q HR 5/5 column. Only one of these binds to cardiolipin-containing liposomes and has thus been identified as the cardiolipin-binding domain of the enzyme. Its amino acid sequence has been determined. The fragment contains 25 amino acids and corresponds to the N-terminal region of the protein. The binding of the fragment of cardiolipin-containing liposomes was inhibited by adriamycin. Another and larger CNBr fragment could be specifically labelled with periodate-oxidized (di-aldehyde) ATP and has thus been identified as the ATP-binding domain. Chemical modification of the basic amino acids Lys and Arg of the enzyme abolished its binding to cardiolipin.