January 30, 2005 | David F. Coppedge

Your Motors Are Turbo-Charged

Think how fast 6000 rpm is.  It would redline on most cars.  Yet you have motors in your body that make that speed look like slow-mo.
    The Japanese have taken great interest in the cellular machine ATP synthase since its rotary operation was discovered in 1996 (see 12/22/2003 entry).  Maybe it’s because they like rotary engines.  ATP synthase is an essential protein complex that generates ATP (adenosine triphosphate), the energy currency of the cell.  Found in the membranes of mitochondria and chloroplasts, it runs on an electrical current of protons, from sunlight (in plants) or digestion (in animals).  It is a reversible engine: it can just as easily generate protons from the dissociation of ATP.  It has five major protein parts, including a rotor, a stator, and a camshaft.  The F0 domain runs like a waterwheel on protons and turns the camshaft.  Three pairs of lobes in the F1 domain catalyze ATP from ADP and phosphate, in a three-phase cycle of input, catalysis, and output.  Each revolution generates 3 ATP.
    Hiroshi Ueno and team, reporting in PNAS,1 have invented new techniques for studying and measuring the tiny motors.  Now, with the aid of a high-speed camera running at 8,000 frames per second, they have clocked the rotational speed of the entire F0F1-ATP Synthase motor at 352 revolutions per second, a whopping 21,120 rpm.
    Although this molecular machine exists in all life forms, they used motors from a thermophilic bacterium.  To monitor the action, the team fastened a microscopic bead to the carousel of c subunits.  At 25° C, it ran at 230 rps.  At 45° C, it ran at 650 rps.  Extrapolating up to 60° C, the organism’s optimum growth temperature, they speculate that it could be running as fast as 1,600 rps – an unbelievable 96,000 rpm – and that with nearly no friction and almost ideal efficiency.  While they caution that reservation is needed whether these “enormous numbers” are actually achieved, they do say with confidence that the rotation rates they measured are much higher than earlier claims.  “It is intriguing to learn,” they say, “whether these rapid rotations are really occurring in living cells.”

1Ueno et al., “ATP-driven stepwise rotation of F0F1-ATP synthase,” Proceedings of the National Academy of Sciences USA, 10.1073/pnas.0407857102, published online before print January 24, 2005.

We owe an apology to our readers.  We have been repeating earlier reports that ATP synthase runs at 6,000 rpm.  That’s like insulting the Ferrari company by watching one moving slowly in a parking lot and claiming it is rated at 10 mph.  We’re sorry for not giving proper credit to the Designer of this high-performance marvel.  Eat your heart out, Charlie.

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Categories: Cell Biology

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