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sliding-filament theory A hypothesis to explain the mechanism of contraction of striated muscle which proposes that the parallel, interdigitated, thick myosin and thin actin filaments slide past one another to varying degrees to shorten the muscle. This is brought about through the sequential formation of crossbridges between the actin and myosin molecules such that the filaments move past one another in a ratchet-like manner. The energy for these processes is provided by the hydrolysis of ATP. The theory is applied to amoeboid and ciliary, as well as muscular movement, and also describes chromosomal movements.