CLONING AND CHARACTERIZATION OF SENC, A GENE INVOLVED IN BOTH AEROBICRESPIRATION AND PHOTOSYNTHESIS GENE-EXPRESSION IN RHODOBACTER-CAPSULATUS

The purple nonsulfur photosynthetic eubacterium Rhodobacter capsulatus is a versatile organism that can obtain cellular energy by several me ans, including the capture of light energy for photosynthesis as well as the use of light-independent respiration, in which molecular oxygen serves as a terminal electron acceptor. In this study, we have identi fied and characterized a novel gene, senC, mutations in which affect r espiration as well as the induction of photosynthesis gene expression, The protein coded by senC exhibits 33% sequence identity to the yeast nucleus-encoded protein SCO1, which is thought to be a mitochondrion- associated cytochrome c oxidase assembly factor, Like yeast SCO1, SenC is required for optimal cytochrome c oxidase activity in aerobically grown R. capsulatus cells, We further show that senC is required for m aximal induction from the puf and puh operons, which encode the struct ural polypeptides of the light-harvesting and reaction center complexe s.