Effect of antibodies to light meromyosin on glycerinated muscle fibres and on actomyosin adenosinetriphosphatases.

The conformation change of light meromyosin influences the myosin and actin interaction, the myosin ATPase activity [22]. Starting from these data the specificity of the phenomenon has been investigated. The effect of LMM1, LMM- and LMM1-antibodies was studied on the isometric tension and relaxation of glycerol extracted muscle fibres. LMM1 was found to relax the fibres isometrically contracted by ATP-Ca2+; anti-LMM and anti-LMM1 markedly accelerated the development of isometric tension and inhibited the relaxation of ATP contracted glycerinated muscle fibres; in the presence of anti-LMM the ATPase rate of glycerinated myofibrils was slightly augmented. These results seem to indicate that LMM1 governs the actin binding site function of myosin and controls its affinity to actin. It is supposed that the reaction of myofibrils with specific LMM antibodies induced a transconformation in the myosin head increasing the affinity to actin of myosin.