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首页> 外文期刊>Biochemistry >Phosphorylation regulates the ADP-induced rotation of the light chain domain of smooth muscle myosin.
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Phosphorylation regulates the ADP-induced rotation of the light chain domain of smooth muscle myosin.

机译:磷酸化调节ADP诱导的平滑肌肌球蛋白轻链结构域的旋转。

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摘要

We have observed the effects of MgADP and thiophosphorylation on the conformational state of the light chain domain of myosin in skinned smooth muscle. Electron paramagnetic resonance (EPR) spectroscopy was used to monitor the orientation of spin probes attached to the myosin regulatory light chain (RLC). Two spectral states were seen, termed here "intermediate" and "final", that are distinguished by a approximately 24 degrees axial rotation of spin probes attached to the RLC. The two observed conformations are similar to those found previously for smooth muscle myosin S1; the final state corresponds to the major conformation of S1 in the absence of ADP, while the intermediate state corresponds to the conformation of S1 with ADP bound. Light chain domain orientation was observed as a function of the MgADP concentration and the extent of RLC thiophosphorylation. In rigor (no MgADP), LC domains were distributed equally between the intermediate state and the final state; upon addition of saturating (3.5 mM) MgADP, about one-third of the LC domains in the final state rotated approximately 20 degrees axially to the intermediate state. The progression of the change in populations was fit to a simple binding equation, yielding an apparent dissociation constant of approximately 110 microM for skinned smooth muscle fibers and approximately 730 microM for thiophosphorylated, skinned smooth muscle fibers. These observations suggest a model that explains the behavior of "latch bridges" in smooth muscle.
机译:我们已经观察到MgADP和硫代磷酸化对皮肤平滑肌中肌球蛋白轻链结构域构象状态的影响。电子顺磁共振(EPR)光谱用于监测连接到肌球蛋白调节轻链(RLC)的自旋探针的方向。看到了两个光谱状态,在这里称为“中间”和“最终”,其特征是连接到RLC的自旋探针的轴向旋转大约24度。观察到的两个构象与先前在平滑肌肌球蛋白S1中发现的构象相似。最终状态对应于在没有ADP的情况下S1的主要构象,而中间状态对应于具有ADP结合的S1的构象。观察到轻链结构域取向是MgADP浓度和RLC硫代磷酸化程度的函数。在严格的条件下(没有MgADP),LC域在中间状态和最终状态之间均等分布。加入饱和(3.5 mM)MgADP后,最终状态下约三分之一的LC结构域轴向轴向旋转约20度到中间状态。群体变化的进展符合一个简单的结合方程式,皮肤平滑肌纤维的表观解离常数约为110 microM,硫代磷酸化皮肤平滑肌纤维的表观解离常数约为730 microM。这些观察结果提出了一个模型,该模型解释了平滑肌中“闩锁桥”的行为。

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