Characterization of ypmQ, an accessory protein required for the expressionof cytochrome c oxidase in Bacillus subtilis

A search of the Bacillus subtilis genome identifies a potential homolog, yp mQ, of the inner mitochondrial membrane protein Sco1 from yeast, Sco1 has b een found to aid the delivery of copper to cytochrome c oxidase, B. subtili s expresses two members of the cytochrome oxidase family, a cytochrome c ox idase that has two copper centers, Cu-A and Cu-B, and a menaquinol oxidase that has only Cu-B. Deletion of ypmQ in B. subtilis depresses expression of cytochrome c oxidase but not menaquinol oxidase, Level of cytochrome c oxi dase recover when copper is added to the growth medium of the Delta ypmQ st rain or when ypmQ is expressed from a plasmid, Neither treatment affects th e amount or activity of menaquinol oxidase. YpmQ in which two conserved cys teines are replaced by serines and a conserved histidine is replaced by ala nine do not complement the deletion of ypmQ even though these mutant forms are found in the membrane extract at a level similar to the wild type prote in. Fire propose that the two cysteines and the histidine are critical for the function of YpmQ and suggest they are involved in copper exchange betwe en YpmQ and the Cu-A site of cytochrome c oxidase.