Dmo2p is required for Cox2p stability and plays a role in mitochondrial redox balance.

Based on available platforms of Saccharomyces cerevisiae mitochondrial proteome and other high throughput studies, we identified the yeast gene DMO2 with a profile of genetic and physical interactions that indicate a putative role in mitochondrial respiration. Dmo2p is a homolog to human DMAC1 with two conserved cysteines in a Cx2C motif. Here, we localized Dmo2p in the mitochondrial inner membrane with the conserved cysteines facing the intermembrane space. The observed phenotypes of the dmo2 null mutant indicate a general function in cellular stress response; the mutant displayed poor growth on non-fermentative media at 37{degrees}C, and in oleate, it is more sensitive to heat and oxidative stress while its overexpression confers resistance to some of the tested stressors. Dmo2p topology and modeled structure suggested a functional redox role for the Cx2C motif sustained by site-directed mutagenesis of both cysteine residues. The respiratory deficiency of dmo2 mutants at 37{degrees}C led to a reduction in cytochrome c oxidase activity (COX) and the formation of bc1-COX supercomplexes; we also observed a rapid turnover of Cox2p, the subunit two of the cytochrome c oxidase complex that harbors the binuclear CuA center. Moreover, Dmo2p co-immunoprecipitated with Cox2p and components of CuA center maturation such as Sco1p and Sco2p; and finally, DMO2 overexpression can suppress cox23 respiratory deficiency, a mutant that has the mitochondrial copper homeostasis impaired. Overall, our data suggest that Dmo2p is required for Cox2p maturation, potentially by aiding proteins involved in copper transport and incorporation into Cox2p.