The myosin motor in muscle generates a smaller and slower working stroke at higher load
The myosin motor in muscle generates a smaller and slower working stroke at higher load
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DOI：
10.1038/nature02380
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发表时间：
2004-04-01
期刊：
影响因子：
64.8
通讯作者：
Lombardi, V
中科院分区：
文献类型：
--
作者：
Reconditi, M;Linari, M;Lombardi, V
肌肉收缩由运动蛋白肌球蛋白 II 驱动，该蛋白短暂地与肌动蛋白丝结合，产生单一的丝位移或“工作冲程”，然后分离并重复该循环。先前已在低负荷下使用分离的肌球蛋白 II 分子测量了冲程大小，结果差异较大 (1-4)，但在肌肉收缩期间电机所承受的较高负荷下则没有测量过冲程大小。在这里，我们使用一种新颖的 X 射线干扰技术 (5,6) 来测量完整肌肉细胞中恒定负载 (7) 下肌球蛋白 II 的工作冲程，从而保留了运动的天然结构和功能。我们表明，在较高负载下，冲程更小且更慢。低负载下的冲程大小可能由结构限制设定(8,9)；在较高负载下，电机在达到此极限之前与肌动蛋白分离。肌球蛋白 II 冲程的负荷依赖性是骨骼肌机械性能和效率的主要分子决定因素。
Muscle contraction is driven by the motor protein myosin II, which binds transiently to an actin filament, generates a unitary filament displacement or 'working stroke', then detaches and repeats the cycle. The stroke size has been measured previously using isolated myosin II molecules at low load, with rather variable results(1-4), but not at the higher loads that the motor works against during muscle contraction. Here we used a novel X-ray-interference technique(5,6) to measure the working stroke of myosin II at constant load(7) in an intact muscle cell, preserving the native structure and function of the motor. We show that the stroke is smaller and slower at higher load. The stroke size at low load is likely to be set by a structural limit(8,9); at higher loads, the motor detaches from actin before reaching this limit. The load dependence of the myosin II stroke is the primary molecular determinant of the mechanical performance and efficiency of skeletal muscle.