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Stepping Rotation of F1-ATPase at Low ATP Concentrations
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[ATP] = 20 nM |
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[ATP] = 200 nM |
At low ATP concentrations, F1 rotates in discrete 120° steps. The stepping rate is proportional to the ATP concentration, indicating that each step is driven by one and only one ATP molecule. In the movie at 20 nM ATP, there is an instant where the F1 motor makes a mistake and steps backward (clockwise). A molecular machine occasionally makes mistakes, and its operation is always stochastic as seen in the figure at left. Because of the stochasic nature, one can never synchronize multiple molecular machines. To analyze their mechanism, therefore, one needs to observe individual molecules closely. |
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