Mitochondrial particles resolved for ion translocation: II. Extraction of cofactors and restoration of activity

Abstract Extraction with a concentrated solution of dibasic potassium hydrogen phosphate, of mitochondrial translocating particles coupled at the third site, yielded a particle which accumulated Sr ++ , Ca ++ , and Mn ++ only when supplemented with cytochrome c . Addition of another, unidentified factor caused a substantial increase in the rate of accumulation of these ions. Although the endogenous cytochrome c had been only partially extracted from these particles, added cytochrome c was required for translocation of Sr ++ , whether energized by oxidation of succinate or by hydrolysis of ATP. This finding confirmed the central role of cytochrome c in the formation of high energy intermediates and compelled the postulate that cytochrome c functions at two different sites in the electron transfer chain.