Turnover of ATP synthase subunits in F1-depleted HeLa and yeast cells

Mitochondrial translation of the Saccharomyces cerevisiae Atp6p subunit of F1–F0 ATP synthase is regulated by the F1 ATPase. Here we show normal expression of Atp6p in HeLa cells depleted of the F1 β subunit. Instead of being translationally down-regulated, HeLa cells lacking F1 degrade Atp6p, thereby preventing proton leakage across the inner membrane. Mammalian mitochondria also differ in the way they minimize the harmful effect of unassembled F1 α subunit. While yeast mutants lacking β subunit have stable aggregated F1 α subunit in the mitochondrial matrix, the human α subunit is completely degraded in cells deficient in F1 β subunit. These results are discussed in light of the different properties of the proteins and environments in which yeast and human mitochondria exist.

► Subunit Atp6p of HeLa cells ATP synthase is not translationally regulated by F1. ► HeLa cells lacking F1 clear mitochondria of newly translated Atp6p by proteolysis. ► Atp6p proteolysis in F1-less cells safeguards against mitochondrial proton leakage. ► F1 α subunit is rapidly degraded in HeLa cells depleted of its partner β subunit.