Identification of the Isoform-specific Interactions between the Tail and the Head of Class V Myosin*
Identification of the Isoform-specific Interactions between the Tail and the Head of Class V Myosin*
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DOI：
10.1074/jbc.m115.693762
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发表时间：
2016-02
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影响因子：
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通讯作者：
Lin-Lin Yao-Lin;M. Shen;Zekuan Lu;M. Ikebe;Xiang-dong Li
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作者：
Lin-Lin Yao-Lin;M. Shen;Zekuan Lu;M. Ikebe;Xiang-dong Li
脊椎动物具有V类肌球蛋白（Myo 5）的三种亚型，Myo 5a，Myo 5 b和Myo 5c，它们参与多种货物的运输。已经确定Myo 5a和Myo 5 b的运动功能受尾部抑制机制调节。在这里，我们发现Myo 5c的运动功能也受到其球状尾结构域（GTD）的抑制，并且这种抑制被高Ca 2+消除，表明尾抑制机制在脊椎动物Myo 5中是保守的。有趣的是，我们发现Myo 5a-GTD和Myo 5c-GTD在抑制运动功能方面是不可互换的，这表明GTD和Myo 5头部之间存在同种型特异性相互作用。为了鉴定亚型特异性相互作用，我们通过交换Myo 5a和Myo 5c的相应区域产生了许多Myo 5嵌合体。我们发现Myo 5a-GTD的H11-H12环被Myo 5c的H11-H12环取代后，能够抑制Myo 5c的ATP酶活性，而Myo 5a-GTD只有在其IQ 1基序被Myo 5a的IQ 1基序取代后才能抑制Myo 5c-S1和Myo 5c-HMM的ATP酶活性。这些结果表明GTD中的H11-H12环和头部中的IQ 1基序决定了GTD和Myo 5头部之间的亚型特异性相互作用。由于IQ 1基序被钙调蛋白包裹，其构象受IQ 1基序序列的影响，我们提出与IQ 1基序结合的钙调蛋白在Myo 5的抑制状态下与GTD的H11-H12环相互作用。
Vertebrates have three isoforms of class V myosin (Myo5), Myo5a, Myo5b, and Myo5c, which are involved in transport of multiple cargoes. It is well established that the motor functions of Myo5a and Myo5b are regulated by a tail inhibition mechanism. Here we found that the motor function of Myo5c was also inhibited by its globular tail domain (GTD), and this inhibition was abolished by high Ca2+, indicating that the tail inhibition mechanism is conserved in vertebrate Myo5. Interestingly, we found that Myo5a-GTD and Myo5c-GTD were not interchangeable in terms of inhibition of motor function, indicating isoform-specific interactions between the GTD and the head of Myo5. To identify the isoform-specific interactions, we produced a number of Myo5 chimeras by swapping the corresponding regions of Myo5a and Myo5c. We found that Myo5a-GTD, with its H11-H12 loop being substituted with that of Myo5c, was able to inhibit the ATPase activity of Myo5c and that Myo5a-GTD was able to inhibit the ATPase activity of Myo5c-S1 and Myo5c-HMM only when their IQ1 motif was substituted with that of Myo5a. Those results indicate that the H11-H12 loop in the GTD and the IQ1 motif in the head dictate the isoform-specific interactions between the GTD and head of Myo5. Because the IQ1 motif is wrapped by calmodulin, whose conformation is influenced by the sequence of the IQ1 motif, we proposed that the calmodulin bound to the IQ1 motif interacts with the H11-H12 loop of the GTD in the inhibited state of Myo5.