Bovine coupling factor 6, with just 14.5% shared identity, replaces subunit h in the yeast ATP synthase

The mammalian mitochondrial ATP synthase is composed of at least 16 polypep tides. With the exception of coupling factor F-6, there are likely yeast ho mologs for each of these polypeptides. There are no obvious yeast homologs of F-6, as predicted from primary sequence comparison of the putative pepti des encoded by the open reading frames in the yeast genome. In this manuscr ipt, we demonstrate that expression of bovine F-6 complements a null mutant in ATP14 gene in yeast Saccharomyces cerevisiae. Subunit h of the yeast AT P synthase is encoded by ATP14 and is just 14.5% identical to bovine F-6. E xpression of bovine F-6 in an atp14 null mutant strain recovers oxidative p hosphorylation, and the ATP synthase is active, although functioning with a lower efficiency than the wild type enzyme. Like subunit h, bovine F-6 is shown to interact mainly with subunit 4 (subunit b), a component of the sec ond stalk of the enzyme. These data indicated the subunit h is the yeast ho molog of mammalian coupling factor F-6.