[Molecular mechanism of muscle contraction: the straightening of the bent actomyosin bond].

A new molecular mechanism of muscle contraction is considered based on the cyclochelate oxyphosphorane structure of the long-lived intermediate in myosin-catalyzed ATP. Mg hydrolysis proposed earlier by the author. The mechanism implies the steric cleavage of the actomyosin bond by the gamma-phosphoryl group of ATP.Mg tightly binding to myosin; the myosin-catalyzed addition of water to the gamma-phosphoryl group to give oxyphosphorane group which sterically allows the formation of a more weak bent (deformed) actomyosin bond; the actin-catalyzed breakdown of the tightly bound oxyphosphorane intermediate into weakly bound products; the straightening of the bent actomyosin bond with the active change of an angle of myosin head attachment, the liberation of the weakly bound products and the displacement of the actin filament. The data are given in favour of an oxyphosphorane structure of the long-lived intermediate.