Saccharomyces cerevisiae Dmo2p is required for the stability and maturation of newly translated Cox2p

Based on available platforms detailing the Saccharomyces cerevisiae mitochondrial proteome and other high-throughput studies, we identified the yeast gene DMO2 as having a profile of genetic and physical interactions that indicate a putative role in mitochondrial respiration. Dmo2p is a homologue to human distal membrane-arm assembly complex protein 1 (DMAC1); both proteins have two conserved cysteines in a Cx₂C motif. Here, we localised Dmo2p in the mitochondrial inner membrane with the conserved cysteines facing the intermembrane space. The respiratory deficiency of dmo2 mutants at 37°C led to a reduction in cytochrome c oxidase (COX) activity (COX) and in the formation of cytochrome bc₁ complex-COX supercomplexes; dmo2 also has a rapid turnover of Cox2p, the second subunit of the COX complex that harbours the binuclear Cu_A centre. Moreover, Dmo2p co-immunoprecipitates with Cox2p and components required for maturation of the Cu_A centre, such as Sco1p and Sco2p. Finally, DMO2 overexpression can suppress cox23 respiratory deficiency, a mutant that has impaired mitochondrial copper homeostasis. Mass spectrometry data unveiled the interaction of Dmo2p with different large molecular complexes, including bc₁-COX supercomplexes, the TIM23 machinery and the ADP/ATP nucleotide translocator. Overall, our data suggest that Dmo2p is required for Cox2p maturation, potentially by aiding proteins involved in copper transport and incorporation into Cox2p.