ATP-Driven Oscillation of Glycerol-Extracted Insect Fibrillar Muscle: Mechano-Chemical Coupling

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Abstract
Synchronous (fibrillar) insect flight muscle oscillates according to a myogenic rhythm. The oscillator is built into the contractile structure, which can oscillate and perform work in a constant chemical environment with ATP as the only source of energy, when it has been isolated by glycerol-extraction. During oscillation, changes in tension follow changes in length with a delay, since contractile activity is switched on and off with a delay by elongation and shortening of the glycerol-extracted fibers (stretch activates, and release of the fibers deactivates, the contractile ATPase). Consequently, sinusoidal stretch and release induce oscillation (driven oscillation) associated with extra ATPase activity. The latter is proportional to the power-output, implying a biochemical Fenn-effect. Power-output and ATPase activity can be increased by raising the concentration of calcium or—at constant chemical conditions—by increasing the frequency orthe amplitude of driven oscillation, demonstrating a mechano-chemical coupling between mechanical performance(product of delayed tension and speed of shortening) and enzymatic activity.

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