[The paramyosin function in glycerinated muscle fibers during blocking with antibodies of its contacts with...

Antibodies to paramyosin (APM) induce a partial decrease of the isometric tension in glycerinated fibres of the Anodonta cygnea catch muscle in the presence of ATP and Ca2+; the myofibrillar Mg2+ ATPase increases concomitantly. Assumedly paramyosin inhibits the cross-bridges unlocking, retaining them mechanically in a locked state. The fibres of barnacle giant muscle in an ATP deficient solution respond to APM by transient isometric tension development. A model for the participation of paramyosin in the contractile process is proposed. In both muscle types paramyosin hinders the functioning of certain elements of the contractile machinery.