来自不同亚型的小肌球蛋白II集合体对机械负荷和ATP浓度的敏感性
Sensitivity of small myosin II ensembles from different isoforms to mechanical load and ATP concentration
摘要：
基于一个详细的跨桥模型的个别肌球蛋白II电机，我们系统地研究了机械负荷和三磷酸腺苷（ATP）浓度的影响，小肌球蛋白II合奏从不同的亚型。对于骨骼肌和平滑肌肌球蛋白II，其通常用于重构细胞收缩性的肌动球蛋白凝胶中，快进运动被限制在具有低机械负荷和高ATP浓度的相空间的小区域，其特征还在于频繁的整体脱离。在高负荷下，这些集合体停滞或向后移动，但向前运动可以通过降低ATP浓度来恢复。相比之下，非肌肉肌球蛋白II亚型，这是在非肌肉细胞的细胞骨架中发现的小合奏，几乎不受ATP浓度的影响，由于结合状态的缓慢动力学。对于所有的亚型，合奏运动的热力学效率随着ATP浓度的降低而增加，但这种影响是弱的非肌肉肌球蛋白II亚型。
英文摘要：
Based on a detailed crossbridge model for individual myosin II motors, we systematically study the influence of mechanical load and adenosine triphosphate (ATP) concentration on small myosin II ensembles made from different isoforms. For skeletal and smooth muscle myosin II, which are often used in actomyosin gels that reconstitute cell contractility, fast forward movement is restricted to a small region of phase space with low mechanical load and high ATP concentration, which is also characterized by frequent ensemble detachment. At high load, these ensembles are stalled or move backwards, but forward motion can be restored by decreasing ATP concentration. In contrast, small ensembles of nonmuscle myosin II isoforms, which are found in the cytoskeleton of nonmuscle cells, are hardly affected by ATP concentration due to the slow kinetics of the bound states. For all isoforms, the thermodynamic efficiency of ensemble movement increases with decreasing ATP concentration, but this effect is weaker for the nonmuscle myosin II isoforms.
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