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首页> 外文期刊>American Journal of Physiology >Cooperative attachment of cross bridges predicts regulation of smooth muscle force by myosin phosphorylation.
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Cooperative attachment of cross bridges predicts regulation of smooth muscle force by myosin phosphorylation.

机译：跨桥的协作连接可预测肌球蛋白磷酸化对平滑肌力的调节。

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Serine 19 phosphorylation of the myosin regulatory light chain (MRLC) appears to be the primary determinant of smooth muscle force development. The relationship between MRLC phosphorylation and force is nonlinear, showing that phosphorylation is not a simple switch regulating the number of cycling cross bridges. We reexamined the MRLC phosphorylation-force relationship in slow, tonic swine carotid media; fast, phasic rabbit urinary bladder detrusor; and very fast, tonic rat anococcygeus. We found a sigmoidal dependence of force on MRLC phosphorylation in all three tissues with a threshold for force development of approximately 0.15 mol P(i)/mol MRLC. This behavior suggests that force is regulated in a highly cooperative manner. We then determined whether a model that employs both the latch-bridge hypothesis and cooperative activation could reproduce the relationship between Ser(19)-MRLC phosphorylation and force without the need for a second regulatory system. We based this model on skeletal muscle in which attached cross bridges cooperatively activate thin filaments to facilitate cross-bridge attachment. We found that such a model describes both the steady-state and time-course relationship between Ser(19)-MRLC phosphorylation and force. The model required both cooperative activation and latch-bridge formation to predict force. The best fit of the model occurred when binding of a cross bridge cooperatively activated seven myosin binding sites on the thin filament. This result suggests cooperative mechanisms analogous to skeletal muscle that will require testing.
机译：肌球蛋白调节轻链（MRLC）的丝氨酸19磷酸化似乎是平滑肌力量发展的主要决定因素。 MRLC磷酸化与作用力之间的关系是非线性的，这表明磷酸化不是调节循环桥的数目的简单开关。我们在慢速，强直性猪颈动脉中重新检查了MRLC磷酸化作用力的关系。快速，阶段性兔膀胱逼尿肌;而且很快，进补的大鼠无囊细胞。我们发现在所有三个组织中，力对MRLC磷酸化的S型依存关系，力发展的阈值约为0.15 mol P（i）/ mol MRLC。这种行为表明以高度协作的方式来调节力量。然后，我们确定了同时使用闩锁桥假设和协同激活的模型是否可以在不需要第二调节系统的情况下重现Ser（19）-MRLC磷酸化与作用力之间的关系。我们基于骨骼肌模型，其中附着的跨桥协同激活细丝以促进跨桥附着。我们发现，这样的模型描述了Ser（19）-MRLC磷酸化和作用力之间的稳态和时程关系。该模型需要协同激活和闩锁桥形成来预测力。当跨桥的结合协同激活细丝上的七个肌球蛋白结合位点时，模型的最佳拟合发生。该结果表明类似于骨骼肌的协作机制需要进行测试。

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