Light chain dependent effects of actin binding on the S-1/S-2 swivel in myosin.
Light chain dependent effects of actin binding on the S-1/S-2 swivel in myosin.
复制标题
肌动蛋白结合对肌球蛋白中 S-1/S-2 旋转的轻链依赖性影响。
DOI：
10.1016/0022-2836(85)90345-6
复制
发表时间：
1985
影响因子：
5.6
通讯作者：
Reisler,E
中科院分区：
文献类型：
--
作者：
Miller,L;Reisler,E
摘要肌球蛋白中的S-1、S-2旋转体在分子的头部和尾部之间提供了一种灵活的连接。我们用有限的蛋白质分解方法研究了旋转体的性质。我们的结果表明，肌动蛋白与重肌球蛋白的结合抑制了S-1 S-2转体的胰凝乳酶和木瓜蛋白酶的切割，并且这种作用依赖于完整的LC-2轻链的存在。肌动蛋白不会减缓使用重的肌球蛋白进行的消化，这些肌球蛋白之前用蛋白酶处理过，将LC-2链切断到17,000或14,000个mr片段。虽然LC-2轻链的完整性似乎是将肌球蛋白头部的肌动蛋白结合效应传递到S-1 S-2旋转所必需的，但钙与17,000 mr LC-2片段的结合仍然可以影响SH 1硫醇基团的化学反应活性。含有完整或断裂LC-2轻链的重肌球蛋白的胰凝乳酶和木瓜蛋白酶消化在5°C到35°C之间都表现出相当的温度敏感性。计算的表观活化能表明，S-1 S-2在肌球蛋白中的旋转可以经历依赖于温度的结构变化，而与LC-2轻链的状态无关。因此，肌动蛋白结合和温度变化都可以诱导S-1/S-2旋转的结构转变。
Abstract The S-1 S-2 swivel in myosin provides a flexible link between the head and tail portions of the molecule. We have investigated the properties of the swivel by employing limited proteolysis methods. Our results indicate that the binding of actin to heavy meromyosin inhibits both the chymotryptic and papain cleavage of the S-1 S-2 swivel, and that this effect is dependent on the presence of intact LC-2 light chains. Actin did not slow digestions carried out using heavy meromyosin previously treated with proteases to nick the LC-2 chains to 17,000 or 14,000 M r fragments. Although the integrity of the LC-2 light chain appears to be required to transmit the effects of actin binding from the myosin head to the S-1 S-2 swivel, the binding of Ca 2+ to the 17,000 M r LC-2 fragment can still affect the chemical reactivity of SH 1 thiol groups. Both chymotryptic and papain digestions of heavy meromyosin containing intact or fragmented LC-2 light chain show substantial temperature sensitivity between 5° C and 35° C. Calculated apparent activation energies for this process indicate that the S-1 S-2 swivel in myosin can undergo temperature-dependent structural changes independently of the state of the LC-2 light chain. Thus, both actin binding and temperature variations can induce structural transitions in the S-1/S-2 swivel.