Abstract
COX19, a nuclear gene of Saccharomyces cerevisiae, was cloned by transformation of a respiratory-deficient mutant from complementation group G188 of a pet mutant collection. The gene codes for an 11-kDa protein (Cox19p) required for expression of cytochrome oxidase. Because cox19 mutants are able to synthesize the mitochondrial and nuclear gene products of cytochrome oxidase, Cox19p probably functions post-translationally during assembly of the enzyme. Cox19p is present in the cytoplasm and mitochondria, where it exists as a soluble intermembrane protein. This dual location is similar to what was previously reported for Cox17p, a low molecular weight copper protein thought to be required for maturation of the CuA center of subunit 2 of cytochrome oxidase. The similarity in their subcellular distribution, combined with the presence of four cysteines in Cox19p that align with a subset of the cysteines in Cox17p, suggests that like the latter, Cox19p may function in metal transport to mitochondria.
Highlights
Cytochrome oxidase (COX)1 is a heteroligomeric complex of the mitochondrial respiratory chain
Phenotype of cox19 Mutants—E708 and N559 are two independent isolates previously assigned to complementation group G188 of a collection of respiratory-deficient strains of S. cerevisiae [5]
The other complexes of the respiratory chain and oligomycin-sensitive ATPase are present in the mutants, indicating that the growth defect stems from the COX deficit
Summary
Cytochrome oxidase (COX) is a heteroligomeric complex of the mitochondrial respiratory chain. Some of the genes code for accessory proteins that operate during different stages of assembly and affect a broad range of events required for expression of fully active COX. These include maturation of the mitochondrially encoded transcript for subunits 1, 2, and 3 [6, 7], translation of the resultant mRNAs (8 –10), and membrane insertion and post-translational processing of subunit 2 [11, 12]. Cox19p has been localized in the intermembrane space of mitochondria, a fraction of the protein is detected in the cytosolic fraction In this respect, Cox19p is similar to Cox17p, which has been implicated in transport of copper to mitochondrial [13]. The primary structure of the Cox19p and its subcellular localization further suggest that it is likely to be involved in metal transport
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