Desensitization of Substrate Inhibition of Acto-H-meromyosin ATPase by Treatment of H-Meromyosin with p-Chloromercuribenzoate

Publisher Website
Google Scholar
Abstract
H-Meromyosin (CMB→βME-H-meromyosin) was prepared by tryptic digestion of myosin, which had been treated with CMB and then β-mercaptoethanol. The relation between the amount of CMB bound to H-meromyosin and the extent of desensitization of the substrate inhibition of acto-H-meromyosin ATPase [EC 3.6.1.3] was investigated. Both the dissociation of acto-H-meromyosin induced by ATP and substrate inhibition decreased with increase in the amount of bound CMB to a minimum value at about 1 mole of CMB bound per mole of H-meromyosin. The substrate inhibition of acto-H-meromyosin ATPase was restored to the original level by complete removal of the bound CMB by further treatment of CMB→βME-H-meromyosin with a large excess of β-mercaptoethanol. The dissociation constant of acto-H-meromyosin in the presence of ATP decreased markedly on modification with CMB, while the maximum ATPase activity at a sufficiently high concentration of F-actin remained essentially unchanged. Acto-H-meromyosin was reconstituted from F-actin and CMB→βME-H-meromyosin, containing less than the stoichiometric amount of bound CMB. Its ATPase activity and the extent of dissociation of acto-H-meromyosin induced by ATP were explained as those of a mixture of unmodified H-meromyosin and CMB→βME-H-meromyosin containing 1 mole of CMB per mole of H-meromyosin. Half of the light chains (g2), with a molecular weight of 18,000, were removed from myosin by treatment with CMB and β-mercaptoethanol. After this treatment, on further incubation of the myosin with a large excess of β-mercaptoethanol, the myosin contained only half of the g2, but the substrate inhibition of acto-H-meromyosin ATPase was restored completely

This publication has 0 references indexed in Scilit: