Respiration-driven proton translocation by yeast mitochondria with differing efficiencies of oxidative phosphorylation

Measurements were made of the stoicheiometry of proton translocation coupled to respiration in mitochondria from Candida utilis where the number of functional energy-conservation sites between intramitochondrial NADH and oxygen was one in a mutant with a novel oxidase (Downie & Garland, 1972), two in sulphate-deficient cells (Haddock & Garland, 1971) or three in glycerol-limited cells (Light & Garland, 1971). The stoicheiometries of protons translocated per atom of oxygen utilized (i.e. →H⁺/2e⁻ ratio; Mitchell, 1966) were close to 2.0, 4.0 and 6.0 respectively. Thus by using the same substrate (intramitochondrial NADH) and oxygen throughout, the →H⁺/2e⁻ ratio is shown to be 2.0 per energy-conservation site when the number of such sites is varied from one to three.