CALCIUM-BINDING TO POLYPEPTIDES OF RAT-LIVER AND ZAJDELA-HEPATOMA MITOCHONDRIAL INNER MEMBRANES

Composition and amount of Ca-45(2+)-binding proteins in the inner memb rane fraction of rat liver and Zajdela hepatoma mitochondria were dete rmined, In the inner membrane of liver mitochondria, three major Ca-45 (2+)-binding polypeptides: a protein of similar to 130 kDa (carbamoyl- phosphate synthetase), a glycoprotein of 43-44 kDa (previously conside red as the calcium uniporter), and 29-30 kDa protein were found, These components were absent (130 kDa component) or relatively reduced (43- 44 kDa and 29-30 kDa components) in the inner membrane of hepatoma mit ochondria. Previously unknown low molecular mass polypeptides, having very high Ca2+-binding ability, were found in the inner membrane of he patoma mitochondria. One of them might be the natural Ca2+-binding inh ibitor of H+-ATPase. (C) 1998 Federation of European Biochemical Socie ties.