Velvarska Hana, Niessing Dierk
Institute of Structural Biology; Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany ; Gene Center and Department of Biochemistry, Ludwig-Maximilians-University, München, Germany.
PLoS One. 2013 Dec 10;8(12):e82065. doi: 10.1371/journal.pone.0082065. eCollection 2013.
Vertebrate type V myosins (MyoV) Myo5a, Myo5b, and Myo5c mediate transport of several different cargoes. All MyoV paralogs bind to cargo complexes mainly by their C-terminal globular domains. In absence of cargo, the globular domain of Myo5a inhibits its motor domain. Here, we report low-resolution SAXS models for the globular domains from human Myo5a, Myo5b, and Myo5c, which suggest very similar overall shapes of all three paralogs. We determined the crystal structures of globular domains from Myo5a and Myo5b, and provide a homology model for human Myo5c. When we docked the Myo5a crystal structure into a previously published electron microscopy density of the autoinhibited full-length Myo5a, only one domain orientation resulted in a good fit. This structural arrangement suggests the participation of additional region of the globular domain in autoinhibition. Quantification of the interaction of the Myo5a globular domain with its motor complex revealed a tight binding with dissociation half-life in the order of minutes, suggesting a rather slow transition between the active and inactive states.
脊椎动物V型肌球蛋白（MyoV）中的Myo5a、Myo5b和Myo5c介导多种不同货物的运输。所有MyoV旁系同源物主要通过其C端球状结构域与货物复合物结合。在没有货物的情况下，Myo5a的球状结构域会抑制其运动结构域。在此，我们报告了来自人类Myo5a、Myo5b和Myo5c球状结构域的低分辨率小角X射线散射（SAXS）模型，这些模型表明这三种旁系同源物的整体形状非常相似。我们确定了Myo5a和Myo5b球状结构域的晶体结构，并提供了人类Myo5c的同源模型。当我们将Myo5a晶体结构对接至先前发表的自抑制全长Myo5a的电子显微镜密度图中时，只有一种结构域取向能很好地匹配。这种结构排列表明球状结构域的其他区域参与了自抑制作用。对Myo5a球状结构域与其运动复合物相互作用的定量分析显示，其结合紧密，解离半衰期约为几分钟，这表明在活性状态和非活性状态之间的转变相当缓慢。
