Cytochrome C Oxidase Assembly Protein 18 (COX18)

COX18 encodes a cytochrome c oxidase (COX)-assembly protein. The S. cerevisiae Cox18 protein catalyzes the insertion of the Cox2 (MTCO2) C-terminal tail into the mitochondrial inner membrane, an intermediate step in the assembly of complex IV of the mitochondrial respiratory chain.

The deduced 333-amino acid protein has a predicted molecular mass of 37.1 kD. COX18 shares 25% amino acid identity with S. cerevisiae Cox18 and shares homology with mitochondrial inner membrane protein Oxa1. Database analysis and comparison to yeast Cox18 and Oxa1 suggested that COX18 has 5 transmembrane domains. Northern blot analysis detected a 3.5-kb transcript in all tissues examined with highest expression in liver, heart, and pancreas.