The N-terminal domain of MYO18A has an ATP-insensitive actin-binding site
The N-terminal domain of MYO18A has an ATP-insensitive actin-binding site
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DOI：
10.1021/bi0475931
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发表时间：
2005-04-26
期刊：
影响因子：
2.9
通讯作者：
Sutoh, K
中科院分区：
文献类型：
--
作者：
Isogawa, Y;Kon, T;Sutoh, K
肌球蛋白XVIII是最近发现的第18类肌球蛋白，其成员包括一个独特的N端结构域、一个在ATP酶位点周围具有不寻常序列的马达结构域、一个IQ基序、一个用于二聚化的分段卷曲螺旋区和一个C端球状尾。为了深入了解这种独特的肌球蛋白的功能，我们对其人类同源物MYO 18 A进行了表征，重点关注其特征性N-末端结构域的功能作用，该结构域包含已知介导蛋白质-蛋白质相互作用的PDZ模块。GFP标记的全长和C-末端截短的MYO 18 A分子在HeLa细胞中表达，表现出与肌动蛋白丝共定位。这些分子的化学交联表明，它们形成稳定的二聚体，正如预期的那样，来自它们假定的卷曲螺旋尾部。各种类型的截短MYO 18 A结构与肌动蛋白丝的共沉淀表明在N-末端结构域中存在ATP不敏感的肌动蛋白结合位点。对N-末端结构域截短结构的进一步研究表明，该肌动蛋白结合位点位于PDZ模块之外，但在该结构域的中间区域内，其与已知的肌动蛋白结合基序没有任何同源性。这些结果意味着，这种二聚体肌球蛋白可能稳定交联肌动蛋白丝的N-末端结构域的两个ATP不敏感的肌动蛋白结合位点的肌动蛋白细胞骨架的高阶组织。
Myosin XVIII is the recently identified 18th class of myosins, and its members are composed of a unique N-terminal domain, a motor domain with an unusual sequence around the ATPase site, one IQ motif, a segmented coiled-coil region for dimerization, and a C-terminal globular tail. To gain insight into the functions of this unique myosin, we characterized its human homologue, MYO18A, focusing on the functional roles of the characteristic N-terminal domain that contains a PDZ module known to mediate protein-protein interaction. GFP-tagged full-length and C-terminally truncated MYO18A molecules that were expressed in HeLa cells exhibited colocalization with actin filaments. Chemical cross-linking of these molecules showed that they form stable dimers as expected from their putative coiled-coil tails. Cosedimentation of the various types of truncated MYO18A constructs with actin filaments indicated the presence of an ATP-insensitive actin-binding site in the N-terminal domain. Further studies on truncated constructs of the N-terminal domain indicated that this actin-binding site is located outside the PDZ module, but within the middle region of this domain, which does not show any homology with the known actin-binding motifs. These results imply that this dimeric myosin might stably cross-link actin filaments by two ATP-insensitive actin-binding sites at the N-terminal domains for higher-order organization of the actin cytoskeleton.