[Functional role of the structural nonequivalence of the F-actin subunits of thin filaments].
According to the model of the actin-containing filaments suggested earlier by Frank and author thin filaments of sceletal muscle can be considered as a linear polymer chain composed of structural units each of which can adopt either of two different structural states -- I (inhibited) and A (activated). The structural unit can be represented by a block of two complementary functional units of the thin filaments. The data available indicate that the length of the A-state is slightly longer than the length of the I-state. In this case the relative amount of the functional units in A- and I-states in thin filaments must depend not only on the Ca2+ concentration in sarcomere, but also on the value of the external force pulling the thin filaments in contracting muscle. It is shown that this property of the thin filaments may provide the molecular basis of Hill-equation and the selfadaption of contractile machinery to the value of the external load on muscle.
D000199:Actins / Q000502:physiology; D002118:Calcium / Q000502:physiology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004734:Energy Metabolism; D008433:Mathematics; D008954:Models, Biological; D008956:Models, Chemical; D009119:Muscle Contraction; D009132:Muscles / Q000378:metabolism; D011487:Protein Conformation; D013816:Thermodynamics
D000199:Actins; D002118:Calcium
Funktsional'naia rol' strukturnoĭ neékvivalentnosti sub'edinits F-aktina tonkikh niteĭ.