= F1-ATPase
{c}
<F1-ATPase> is the catalytic, water-exposed sector of <ATP synthase>. In the isolated sector, <ATP hydrolysis> can drive rotation of a central shaft within a ring containing alternating alpha and beta subunits. In the complete membrane-coupled <enzyme>, rotation driven by the <proton-motive force> can instead support <ATP> synthesis. The direction depends on the coupled chemical and mechanical driving forces. <Molecular Biology of the Cell, 4th edition by Bruce Alberts and others>[Chapter 14, ATP Synthase: reversible coupling of proton flow and ATP chemistry]{ref}
A direct experiment attached a fluorescent <actin filament> to the central gamma subunit and immobilized the surrounding assembly. On adding <ATP>, the filament rotated, making nanometre-scale motor action visible through a much larger pointer. This demonstrated rotation during hydrolysis; demonstrating membrane-driven synthesis requires the additional membrane sector and an appropriate driving gradient. <Direct observation of the rotation of F1-ATPase by Hiroyuki Noji and others>[1997, abstract: fluorescent actin filament marker on gamma and ATP-driven rotation]{ref}
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