Bechet J J, d'Albis A
Eur J Biochem. 1985 Jan 2;146(1):117-23. doi: 10.1111/j.1432-1033.1985.tb08627.x.
The ATPase activities of acto-heavy meromyosin and of acto-myosin minifilaments have been compared under the same conditions at low ATP (0.1 mM) and at several KC1 concentrations. The activities, which are strongly salt-dependent in both systems, have been found to be similar at high ionic strength (about 0.16 M) but different at lower ionic strength (0.06-0.07 M). Under this last condition, the catalytic constants kcat and Km are lower for acto-myosin minifilaments than for acto-heavy meromyosin ATPase. In addition, at low ionic strength, any decrease in the concentration of any of the ionic species (ATP, citrate, etc.) induces an increase in the interaction strength between myosin and actin filaments, as revealed by the Km changes. The presence of the troponintropomyosin complex and of Ca2+ also enhances the strength of this interaction. On the other hand, the occurrence of particular interactions between F-actin and myosin minifilaments is further substantiated by the phenomenon of superprecipitation which occurs when the ATP concentration decreases. The favourable effect of the organized structure of the myosin minifilaments on the ATPase activity of actomyosin is discussed.
在低ATP（0.1 mM）以及几种KCl浓度条件下，已对肌动蛋白-重酶解肌球蛋白和肌动球蛋白微丝的ATP酶活性进行了比较。在这两种体系中，活性都强烈依赖于盐浓度，发现在高离子强度（约0.16 M）时两者相似，但在较低离子强度（0.06 - 0.07 M）时有所不同。在最后这种条件下，肌动球蛋白微丝的催化常数kcat和Km低于肌动蛋白-重酶解肌球蛋白ATP酶。此外，在低离子强度下，任何离子种类（ATP、柠檬酸盐等）浓度的降低都会导致肌球蛋白与肌动蛋白丝之间相互作用强度增加，这可通过Km的变化得以揭示。肌钙蛋白-原肌球蛋白复合物和Ca2+的存在也会增强这种相互作用的强度。另一方面，当ATP浓度降低时会出现超沉淀现象，这进一步证实了F - 肌动蛋白与肌球蛋白微丝之间存在特定的相互作用。文中讨论了肌球蛋白微丝的组织结构对肌动球蛋白ATP酶活性的有利影响。
