Bovine Coupling Factor 6, with Just 14.5% Shared Identity, Replaces Subunit h in the Yeast ATP Synthase

Abstract

The mammalian mitochondrial ATP synthase is composed of at least 16 polypeptides. With the exception of coupling factor F6, there are likely yeast homologs for each of these polypeptides. There are no obvious yeast homologs of F6, as predicted from primary sequence comparison of the putative peptides encoded by the open reading frames in the yeast genome. In this manuscript, we demonstrate that expression of bovine F6 complements a null mutant in ATP14 gene in yeast Saccharomyces cerevisiae. Subunit h of the yeast ATP synthase is encoded by ATP14 and is just 14.5% identical to bovine F6. Expression of bovine F6 in an atp14 null mutant strain recovers oxidative phosphorylation, and the ATP synthase is active, although functioning with a lower efficiency than the wild type enzyme. Like subunit h, bovine F6 is shown to interact mainly with subunit 4 (subunit b), a component of the second stalk of the enzyme. These data indicated the subunit h is the yeast homolog of mammalian coupling factor F 6.