IDENTIFICATION OF A 20-KDA PROTEIN WITH CALCIUM-UPTAKE TRANSPORT ACTIVITY - RECONSTITUTION IN A MEMBRANE MODEL

This paper presents results of experiments designed to further purify the membrane system involved in mitochondrial calcium transport. A par tially purified extract, which transported calcium with a specific act ivity of 1194nmol Ca-45(2+)/mg protein/5min, was used to obtain mouse hyperimmune serum. This serum inhibited calcium uptake both in mitopla sts and in vesicles reconstituted with mitochondrial proteins containi ng cytochrome oxidase. Western blot analysis of the semipurified fract ion showed that the serum recognized specifically two antigens of 75 a nd 20 kDa. Both antibodies were purified by elution from the nitrocell ulose sheets and their inhibition capacity was analyzed. The antibody that recognized the 20-kDa protein produced a higher degree of inhibit ion than the other one.