Structural Biology Laboratory, Nara Institute of Science and Technology, Nara, Japan.
EMBO J. 2011 Jun 3;30(13):2734-47. doi: 10.1038/emboj.2011.177.
Myosin-X is an important unconventional myosin that is critical for cargo transportation to filopodia tips and is also utilized in spindle assembly by interacting with microtubules. We present a series of structural and biochemical studies of the myosin-X tail domain cassette, consisting of myosin tail homology 4 (MyTH4) and FERM domains in complex with its specific cargo, a netrin receptor DCC (deleted in colorectal cancer). The MyTH4 domain is folded into a helical VHS-like structure and is associated with the FERM domain. We found an unexpected binding mode of the DCC peptide to the subdomain C groove of the FERM domain, which is distinct from previously reported β-β associations found in radixin-adhesion molecule complexes. We also revealed direct interactions between the MyTH4-FERM cassette and tubulin C-terminal acidic tails, and identified a positively charged patch of the MyTH4 domain, which is involved in tubulin binding. We demonstrated that both DCC and integrin bindings interfere with microtubule binding and that DCC binding interferes with integrin binding. Our results provide the molecular basis by which myosin-X facilitates alternative dual binding to cargos and microtubules.
肌球蛋白-X 是一种重要的非传统肌球蛋白，对于货物向丝状伪足尖端的运输至关重要，并且通过与微管相互作用也用于纺锤体组装。我们介绍了一系列肌球蛋白-X 尾部结构域盒的结构和生化研究，该盒由肌球蛋白尾部同源物 4（MyTH4）和 FERM 结构域与它的特定货物——神经生长因子受体 DCC（结直肠癌缺失）组成。MyTH4 结构域折叠成一个螺旋 VHS 样结构，并与 FERM 结构域相关联。我们发现 DCC 肽与 FERM 结构域的亚结构域 C 槽之间存在一种意想不到的结合模式，与先前在放射粘连分子复合物中发现的β-β 关联不同。我们还揭示了 MyTH4-FERM 盒与微管 C 端酸性尾巴之间的直接相互作用，并确定了 MyTH4 结构域中的一个带正电荷的斑点，该斑点参与微管结合。我们证明 DCC 和整合素的结合都干扰微管结合，并且 DCC 结合干扰整合素结合。我们的结果提供了分子基础，说明肌球蛋白-X 如何促进对货物和微管的替代双重结合。
