Molecular Organization and Regulation of the Protonmotive System of Mammalian ATP Synthase

Abstract

In bacteria the H⁺ translocating membrane sector (F_O) of the F₀, F₁ H⁺ ATP synthase is composed of three subunits (a, b, and c of the E. Coli enzyme (1). In mitochondria more than three proteins appear to constitute the F_o and stalk sectors (1), which are involved in H⁺ conduction and/or coupling of H⁺ translocation to the catalytic process in the F₁ moiety (Table 1) (2,3). Two of these are the products of the mitochondrial genoma:the ATPase 6, homologous to subunit a of E. Coli and likely to be involved as this (4–7) in H⁺ conduction, and A6L in mammals (aapl in yeast), whose function is as yet unknown (1). Other 5 proteins have been identified in the mammalian enzyme which are encoded by nuclear genes (8,9). These include subunit c which is directly involved in H⁺ conduction (10,11), OSCP and F₆ which contribute to connection of F₁ with F_O (1).