CALDESMON INHIBITS THE COOPERATIVE TURNING-ON OF THE SMOOTH-MUSCLE HEAVY-MEROMYOSIN BY TROPOMYOSIN-ACTIN
CALDESMON INHIBITS THE COOPERATIVE TURNING-ON OF THE SMOOTH-MUSCLE HEAVY-MEROMYOSIN BY TROPOMYOSIN-ACTIN
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DOI：
10.1021/bi00449a023
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发表时间：
1989-11-14
期刊：
影响因子：
2.9
通讯作者：
CHACKO, S
中科院分区：
文献类型：
--
作者：
HORIUCHI, KY;CHACKO, S
纯化了具有肌动蛋白/钙调素结合结构域的钙调素的38 kDa胰凝乳蛋白酶片段，并用于研究钙调素抑制肌动球蛋白ATP酶的机制。完整的caldesmon抑制acto-HMM ATP酶，虽然它导致HMM与肌动蛋白的结合增加，推测是由于HMM的S-2区和位于肌动蛋白丝上的caldesmon之间的相互作用。缺少S-2结合结构域的38-kDa片段抑制acto-HMM ATP酶和HMM与肌动蛋白的结合。ATP酶和HMM与肌动蛋白的结合。ATP酶和HMM结合到肌动蛋白平行减少增加38 kDa的片段结合到肌动蛋白。在原肌球蛋白存在的情况下，ATP酶活性下降速度比HMM与肌动蛋白结合的速度更快。完整的钙调蛋白或38-kDa片段与肌动蛋白的结合抑制了NEM·S-1协同开启原肌球蛋白-肌动蛋白，NEM·S-1在ATP存在下形成严格的复合物。在38-kDa片段存在下，僵硬复合物对acto-HMM ATP酶的合作开启的缺乏与HMM与原肌球蛋白-肌动蛋白结合的抑制有关。向原肌球蛋白-肌动蛋白-钙调蛋白中加入NEM·S-1引起钙调蛋白诱导的HMM与肌动蛋白的结合逐渐减少。钙调素恢复了钙调素诱导的HMM与原肌球蛋白-肌动蛋白的结合，但它对acto-HMM ATP酶只有轻微的影响。这些数据表明，合作打开的平滑肌原肌球蛋白-肌动蛋白的僵硬债券调制的相互作用的钙调蛋白，原肌球蛋白，和钙调蛋白的细丝。
The 38-kDa chymotryptic fragment of caldesmon, which possesses the actin/calmodulin binding domain, was purified and utilized to study the mechanism for the inhibition of acto-myosin ATPase by caldesmon. The intact caldesmon inhibited the acto-HMM ATPase although it caused an increase in the binding of HMM to actin, presumably due to the interaction between the S-2 region of HMM and the caldesmon located on the actin filament. The 38-kDa fragment, which lacks the S-2 binding domain, inhibited both the acto-HMM ATPase and the HMM binding to actin. The ATPase and the HMM binding to actin. The ATPase and the HMM binding to actin decreased in parallel on increasing the 38-kDa fragment bound to actin. In the presence of tropomyosin, the ATPase activity fell more rapidly than did the HMM binding to actin. Binding of intact caldesmon or 38-kDa fragment to actin inhibited the cooperative turning-on tropomyosin-actin by NEM.cntdot.S-1, which forms rigor complexes in the presence of ATP. The absence of cooperative turning-on of the acto-HMM ATPase by rigor complexes in the presence of 38-kDa fragment was associated with an inhibition of the binding of HMM to tropomyosin-actin. Addition of NEM.cntdot.S-1 to tropomyosin-actin-caldesmon caused a gradual decrease in the caldesmon-induced binding of HMM to actin. The calmodulin restored the caldesmon-induced binding of HMM to tropomyosin-actin, but it had only a slight effect on the acto-HMM ATPase. These data suggest that the cooperative turning-on of the smooth muscle tropomyosin-actin by rigor bonds is modulated by the interaction of caldesmon, tropomyosin, and calmodulin on the thin filament.