Mutagenesis screen of Saccharomyces cerevisiae Cox11p.
Graham Banting, D. Moira Glerum
Medical Genetics, University of Alberta, 833MedSci, Edmonton, AB, T6G 2H7, Canada
The biogenesis of the mitochondrial enzyme complexes that carry out oxidative phosphorylation is not well understood. Cytochrome oxidase (COX) is the final acceptor in the mitochondrial respiratory chain and studies in the yeast S. cerevisiae have identified a number of gene products that are required for the assembly of this multi-subunit complex. Three of these assembly factors (Cox17p, Sco1p and Cox11p) are involved in the procurement of the copper prosthetic groups, but their precise mechanisms of action have not been well elucidated. Cox11p is a mitochondrial inner membrane protein that is essential for proper COX assembly. Cox11p has previously been shown to be a copper binding protein and has been implicated in the formation of the CuB site within Cox1p. In an effort to elucidate a precise function for Cox11p, we have undertaken a mutagenesis scan of the protein. Here we report the characterization of twenty five mutant alleles of Cox11p, generated using either site-directed or random mutagenesis. Of the sixteen conserved residues targeted, five were dispensable for Cox11p function, while the remaining 11 displayed a variety of COX deficient phenotypes. Interestingly, the mitochondrial cytochrome spectra from several of the mutants show a shifted aa3 peak, suggesting an abnormal heme environment due to an improperly assembled COX enzyme. Further biochemical characterization of these cox11 mutants will be presented.
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