Actin-induced local conformational change in the myosin molecule. II. Conformational change around the S2 thiol group related to the essential intermediate of ATP hydrolysis

Journal of Biochemistry
T Kameyama

Abstract

The effect of F-actin on the conformation around a specific thiol group, S2, in heavy meromyosin was investigated. The extent of the change was estimated from the residual activity of Ca2+-ATPase after modifying the thiol with N-ethylmaleimide (NEM). Experiments were carried out with a modified heavy meromyosin (HMM), in which S1 had been blocked with NEM, to observe the reactivity of S2 alone. 1. F-Actin markedly increased the ATP-induced conformational change around S2, but did not affect the adenylyl imidodiphosphate (AMPPNP)-induced change, and markedly supressed the adenylyl methylenediphosphate (AMPPCP)-induced change. 2. The initial burst of HMM ATPase was retained after the modification of S1. Replacement of Mg2+ with Mn2+ in the medium reduced the cooperative action of F-actin and ATP with concomitant loss of the initial burst. 3. Nevertheless, F-actin was capable of activating the steady-state ATPase activity of HMM even in the presence of Mn2+. 4. The degree of activation by F-actin of the ATP-induced increase in the reactivity of S2 did not parallel that of the steady-state ATP splitting, when the KCl concentration of the medium was varied. The results indicate that the actin-induced local conformational change in t...Continue Reading

Citations

Jan 1, 1986·CRC Critical Reviews in Biochemistry·R Cooke
Dec 1, 1981·European Journal of Biochemistry·H P PrinceC Turner
Apr 1, 1981·Biochimie·R KassabE Audemard
May 20, 1998·Biophysical Journal·E Burmeister GetzP R Selvin

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