ATP synthase rotational

Figure 5.19 Binding-change mechanism for ATP synthase. Rotation of the y subunit inter-converts the three-(3 subunits. The subunit in the tight (T) form contains newly synthesized ATP that cannot be released. Rotation by 120° converts it to the open (O) form, from which ATP can be released, allowing it to bind ADP and P, to begin a new cycle. (From Berg et al., 2001. Reproduced with permission from W.H. Freeman and Co.)...

Parallels between everyday mechanisms and cellular processes extend also to myosin head groups racheting to actin subunits to produce the sliding filaments of skeletal muscle (see Perry, 1997), rotary motors for bacterial flagella (see Armitage, 1997) or movements along microtubules, powered by the proton motive force or ATP (see also Block, 1997). The existence of a mitochondrial rotary motor has recently been established. Boyer s proposal that the y subunit of the mitochondrial ATP synthase rotated within the other subunits has been vindicated by X-ray crystallography (Walker, 1997) and direct demonstration of the rotation. 

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