CYC2P IS REQUIRED FOR MAINTAINING IONIC STABILITY AND EFFICIENT CYTOCHROME-C IMPORT AND MITOCHONDRIAL-FUNCTION IN SACCHAROMYCES-CEREVISIAE

A previous study demonstrated that Cyc2p from Saccharomyces cerevisiae is a mitochondrial protein and that cyc2 mutants contained only appro ximately 20% of the normal levels of cytochrome c due to a partial def iciency in mitochondrial import of apo-cytochrome c. We report herein that deletion of the entire gene results in defective mitochondrial fu nction, as revealed by diminished growth on media containing nonfermen table carbon sources. This defect is exacerbated in hyper-ionic KCI me dia and at higher incubation temperatures, but is suppressed on media containing sorbitol, a non-ionic compound. We suggest that Cyc2p serve s to maintain the osmotic stability of mitochondria, and its defect is exacerbated by KCI. (C) 1998 Federation of European Biochemical Socie ties.