Posted on 02/25/2005 1:43:30 PM PST by DannyTN
Clutch Enables Your Motors to Achieve 100% Efficiency 02/23/2005
Those little ATP synthase motors (see 01/30/2005 entry) in your body and (in all living cells) made news again in Nature1 last week. Scientists in Tokyo performed an ingenious set of experiments to measure the efficiency of the F1 synthesizing domain. They attached a tiny magnet to the camshaft so that they could turn it with electromagnets at will, and they carefully measured the amount of ATP synthesized or hydrolyzed as the motor turned anticlockwise or clockwise under their control. In the hydrolysis cycle, they found that the motor did not waste ATP; each molecule was successfully hydrolyzed with perfect efficiency, to the limits of their detection.
A particular focus of their investigation was the role of the eta subunit, which is attached to the gamma camshaft. During hydrolysis, the “downhill” function, it did not seem to matter whether eta was present or absent. But in the “uphill” process (synthesizing ATP), it made a dramatic difference. Without eta, each rotation produced, on average, only one product, but with it, they got three per revolution, with at least 77% efficiency. The actual efficiency was probably higher, but was hard to measure for such small entities. In best cases, it was 100%, they said: “Therefore our data point to an excellent mechanochemical coupling efficiency. In the best cases, we observed the postulated value of three ATPs synthesized per turn.”
“These results are consistent with the ubiquity of this strategic enzyme that fuels most of the energy consuming biological processes,” they said (emphasis added in all quotes). “The present work reveals the unexpected importance of the eta-subunit in the synthesis of ATP.” Though its precise function remains to be discovered, it was known to play a regulatory role; now, this team suspects it acts like a structural switch or clutch to lock the enzyme into synthesis mode. Without it, the tiny motor undergoes wasteful slippage.
As a reminder to recent readers, you can find a wonderful animation of this molecular machine on the website of German biochemist Wolfgang Junge. It is labeled “F0F1-ATPSynthase (animation)” See also his Model Schematic.
By now, you expect our next observation: “The authors made no reference to evolution in their paper.” They are treating these devices as actual mechanical motors, with stator, rotor, camshaft, and purposeful function, achieving performance stats beyond the dreams of human engineering. Eat your heart out, David Hume.
Next headline on: Cell Biology • Amazing Stories
Your Motors Are Turbo-Charged 01/30/2005
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 lifeforms, 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.”
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.
Next headline on: Cell Biology • Amazing Stories
Intelligent ping.
Opinions vary.
Welcome back to the idiots on parade.
Yeah, but it's not nearly as much fun.(grin)
Btw, which developed first, cell nuclei or cell walls and membranes?
Thanks. I should fit right in.
Well said.
Welcome back, my friend ;)
And you guys.
[Clack][Clack]
Welcome back!! :^)
®
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