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ATP Synthesis:- ATP Synthase Has Two Functional Domains, Fo and F1

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  708

2026-06-21

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ATP Synthesis:- ATP Synthase Has Two Functional Domains, F_o and F₁

Mitochondrial ATP synthase is an F-type ATPase similar in structure and mechanism to the ATP synthases of chloroplasts and eubacteria. This large enzyme complex of the inner mitochondrial membrane catalyzes the formation of ATP from ADP and Pi, accompanied by the flow of protons from the P to the N side of the mem brane (Eqn 19–10). ATP synthase, also called Complex V, has two distinct components: F₁, a peripheral membrane protein, and F_o (o denoting oligomycin-sensitive), which is integral to the membrane. F₁, the first factor recognized as essential for oxidative phos phorylation, was identified and purified by Efraim Racker and his colleagues in the early 1960s. In the laboratory, small membrane vesicles formed from inner mitochondrial membranes carry out ATP syn thesis coupled to electron transfer. When F₁ is gently extracted, the “stripped” vesicles still contain intact respiratory chains and the F_o portion of ATP synthase.

The vesicles can catalyze electron transfer from NADH to O₂ but cannot produce a proton gradient: Fo has a proton pore through which protons leak as fast as they are pumped by electron transfer, and without a proton gradient the F₁-depleted vesicles cannot make ATP. Isolated F₁ catalyzes ATP hydrolysis (the reversal of syn thesis) and was therefore originally called F1ATPase. When purified F₁ is added back to the depleted vesicles, it reassociates with F_o, plugging its proton pore and restoring the membrane’s capacity to couple electron transfer and ATP synthesis.