| dc.description.abstract | Copper is required for the assembly and activity of cytochrome c oxidase (CcO), the terminal enzyme of the mitochondrial respiratory chain. As a multi-subunit metalloprotein, CcO biogenesis involves many assembly factors necessary for the proper association of protein subunits and insertion of cofactors. Although the identity of these assembly factors has long been known, their precise roles in CcO biogenesis have remained unknown. Here we investigated the role of Coa4, an evolutionarily conserved CcO assembly factor with unknown function. We found that coa4Δ yeast cells have a respiratory growth phenotype correlated with impaired CcO assembly and activity, as well as reduced mitochondrial copper levels, all of which can be alleviated by exogenous copper supplementation. These results suggest that disrupted copper transport to CcO is the biochemical basis of the respiratory deficiency of coa4Δ cells. Copper delivery to CcO occurs in a bucket brigade fashion via copper delivery pathway proteins. To place Coa4 in the copper delivery pathway, we performed a candidate-based suppression screen with 15 genes implicated in CcO assembly. Overexpression of COX11, a metallochaperone involved in copper delivery to the CcO subunit Cox1, rescued the respiratory growth of coa4Δ cells, suggesting that Coa4 acts upstream of Cox11. The sub-mitochondrial localization and sequence analyses of Coa4 suggested a redox role in the copper delivery process. In support of this idea, we found that glutathione supplementation and hypoxia treatment each rescued the respiratory growth of coa4Δ cells. Taken together, these results uncover Coa4 as a novel member of the copper delivery pathway to the Cox1 subunit of CcO. | |
