The nuclear-coded subunits of yeast cytochrome c oxidase. III. Identification of homologous subunits in yeast, bovine heart, and Neurospora crassa cytochrome c oxidases.

Sequences for the NH2-terminal halves of subunits IV, V, VI, VII, and VIIa from yeast cytochrome c oxidase have been determined and used to identify homologous subunits in bovine heart and Neurospora crassa cytochrome c oxidases. In conjunction with the complete sequence of subunit VIII (S. D. Power, M. A. Lochrie , T. E. Patterson, and R. O. Poyton (1984) J. Biol. Chem. 259, 6571-6574), we have been able to identify counterparts to yeast subunits IV, V, VI, and VIII in bovine heart cytochrome c oxidase and counterparts to yeast subunits IV and V in Neurospora crassa cytochrome c oxidase. The sequences of these nuclear-coded subunits are conserved between species at a level of 30-50%. Thus, they are conserved to the same extent as the three mitochondrially coded subunits (I, II, and III). The similar degree of homology between species for both the nuclear and mitochondrially coded subunits of cytochrome c oxidase suggests that both sets of polypeptides are conserved coordinately and are, therefore, important components of the functional holoenzyme.