Sally Hansen, Utah Valley University
Chemistry
Cytochrome c oxidase (CcO) or complex IV is the terminal component of the electron transport chain. In eukaryotic organisms, CcO is composed of 12-13 subunits. The core of eukaryotic CcO contains three mitochondrially encoded subunits that comprise the catalytic core of the complex and several gene products encoded for by the nucleus (1). Essential to the redox function of CcO are several critical cofactors: two hemes and two copper centers (2). The crystal structure of CcO has led us to several insights about its structural components and catalytic activity (3). However, a large set of nuclear gene products are essential for CcO activity that are not part of the structural machinery of the complex (4,5). These components have been implicated in various stages of CcO assembly including, heme processing and insertion (6), CuA and CuB site delivery and insertion (7), subunit processing and subunit assembly (8,9). Among them are well characterized CcO assembly factors that involve the biogenesis of the CuA and CuB sites in CcO. Sco I, Cox17, Cox 11 and Cox23 are all essential to CcO activity and have properties that appear to be critical to the maturation of the CuA and CuB sites(10-13). Cmc4 appears to be involved in cytochrome c oxidase biogenesis. Peroxide phenotypes have been linked to cytochrome c oxidase assembly (14). Saccharomyces cerevisiae strains lacking CMC4 were found to exhibit peroxide resistance when compared wild type parental stains. Resistance was seen in liquid culture and in media containing glucose and glycerol. These results may indicate that cytochrome c oxidase assembly is altered in CMC4 deletion stains.