Cross-bridge movement in muscle and the conformation of the myosin hinge.
Cross-bridge movement in muscle and the conformation of the myosin hinge.
复制标题
肌肉的跨桥运动和肌球蛋白铰链的构象。
DOI：
10.1002/9780470720752.ch11
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Tsong,TY
中科院分区：
文献类型：
--
作者：
Harrington,WF;Ueno,H;Tsong,TY
在肌肉中的力产生机制进行了讨论，它表明，在S-2链接的循环跨桥的螺旋线圈过渡是兼容的物理和化学性质的肌球蛋白分子的这个区域。热熔融和温度跳跃实验表明，轻肌球蛋白-重肌球蛋白（LMM-HMM）铰链结构域的S-2是一个低的热稳定性的一段。该区域可以在与等距收缩肌肉突然缩短或拉伸时观察到的快速恢复张力瞬态相当的时间尺度上经历α-螺旋-无规卷曲转变。在静止、僵硬和活化溶剂中对甘油化肌纤维和肌纤维进行的交联和酶探针研究表明，S-2铰链区内的多肽链经历了构象转变，蛋白水解敏感的结构，当S-现在人们普遍认为肌肉收缩的基本机制包括一个主动滑动过程在肌动蛋白和肌球蛋白的细丝之间发育。基于结构、生物化学和生理学研究，也有大量可靠的证据表明，负责产生收缩力的元件存在于肌球蛋白分子的横桥--突出端，其含有该分子的ATP酶活性球状头部（S-1亚基）。当肌肉受到刺激收缩时，肌动蛋白和肌球蛋白细丝相互滑动数百纳米，ATP以需要交叉桥重复连接和分离的速度被切割。对分离的S-1亚基与肌动蛋白丝在体外相互作用的生化研究表明，每次S-1进行结合和释放时，ATP都被切割;切割的最大速率接近于细胞中跨桥的周期时间。
The force-generating mechanism in muscle is discussed and it is shown that a helix-coil transition in the S-2 link of the cycling cross-bridge is compatible with the physical and chemical properties of this region of the myosin molecule. Thermal melting and temperature-jump experiments are described demonstrating that the light meromyosin-heavy meromyosin (LMM—HMM) hinge domain of S-2 is a segment of low thermal stability. This region can undergo a-helix—random coil transitions on a time-scale comparable to the quick-recovery tension transient observed when isometrically contracting muscle is abruptly shortened or stretched. Cross-linking and enzyme probe studies of glycerinated muscle fibres and myofibrils in resting, rigor and activating solvents suggest that the polypeptide chains within the hinge region of S-2 undergo a conformational transition to a more open, proteolytically sensitive structure when the S-2 link is released from the thick filament surface.There is now general agreement that the basic mechanism of muscle contraction involves an active sliding process developed between filaments of actin and myosin. There is also a large body of well-established evidence, based on structural, biochemical and physiological studies, that the elements responsible for the generation of contractile force reside in the crossbridges—the projecting ends of the myosin molecules, which contain the ATPase-active globular heads (S-1 subunits) of the molecule. When muscle is stimulated to contract, the actin and myosin filaments slide past each other by several hundreds of nanometres and ATP is cleaved at a rate which requires repetitive attachment and detachment of the cross-bridges. Biochemical studies of the interaction of isolated S-1 subunits with actin filaments in vitro reveal that ATP is cleaved each time S-1 undergoes binding and release; the maximum rate of cleavage approximates the cycle time of the cross-bridge in