[Molecular mechanisms of muscle contraction]

Studying the mechanism of muscular contraction not even in one of the cases deriving from 50 sources could be obtained a myosin preparation free of phosphate. Therefore the aim of the authors was to elaborate methods which provided means for producing preparations of an endogenous P content that approached the P content of myosins of live sources. The phosphoryl groups of myosin may be released by incubating these preparations with F-actin. The actin attaches to the interaction domain of myosin and upon its effect P migrates within the myosin molecule from the site of phosphorylation to the interaction domain. At the interaction the myosin attaches to the actin through the phosphoryl group subsequently the myosin head turns from 90 degrees to 45 degrees consequently the actin-filament moves to a 12 mm distance towards the center of the sarcomer. When the myosin-actin-phosphoryl bridge ceases to be the P attaches transiently to the actin and the anorganic phosphate releases from the actin. The active center of myosin is filled again with the gamma phosphoryl group of ATP and the head returns simultaneously to the resting position of 90 degrees.