Oliver T N, Berg J S, Cheney R E
Department of Cell and Molecular Physiology, School of Medicine, University of North Carolina at Chapel Hill, 27599-7545, USA.
Cell Mol Life Sci. 1999 Oct 15;56(3-4):243-57. doi: 10.1007/s000180050426.
In addition to the conventional myosins (class II) required for processes such as muscle contraction and cytokinesis, the myosin superfamily of actin-based motor proteins includes at least 14 'unconventional' classes. These unconventional myosins are defined by myosin-like head (motor) domains attached to class-specific tail domains that differ greatly from those of myosin-II. The unconventional myosins account for almost two-thirds of the 28 or more myosin genes currently believed to be expressed in humans and 80-90% of the approximately 10 or more myosin genes expressed in a typical nonmuscle cell. Although these members of the myosin superfamily have not been as intensively investigated as the conventional myosins, unconventional myosins are known or believed to power many forms of actin-based motility and organelle trafficking. The presence of signaling domains such as kinase domains, SH3 domains, PH domains or GTPase-activating domains in the tails of unconventional myosins indicates that these proteins can also be components of signal transduction pathways. Since several classes of the myosin superfamily have been found only in lower eukaryotes or plants (VIII, XI, XIII and XIV), in this review we will focus on the structures and properties of the unconventional myosins found in multicellular animals (excluding classes I and V, which have been reviewed elsewhere recently). Special attention will be focused on the three classes of unconventional myosins that can cause deafness in mouse or humans when mutated. In addition, we discuss the discovery of a pair of intriguing domains, the Myosin Tail Homology 4 (MyTH4) and FERM (band 4.1, Ezrin, Radixin, Moesin) domains, that are present in the tails of otherwise very different myosins as well as a plant kinesin-like protein. Recent progress in the identification of novel unconventional myosins will also be summarized.
除了肌肉收缩和胞质分裂等过程所需的传统肌球蛋白（II类）外，基于肌动蛋白的运动蛋白肌球蛋白超家族还包括至少14个“非传统”类别。这些非传统肌球蛋白由附着在类别特异性尾部结构域上的类肌球蛋白头部（运动）结构域定义，这些尾部结构域与肌球蛋白II的尾部结构域有很大差异。非传统肌球蛋白占目前认为在人类中表达的28个或更多肌球蛋白基因的近三分之二，以及在典型非肌肉细胞中表达的约10个或更多肌球蛋白基因的80 - 90%。尽管肌球蛋白超家族的这些成员没有像传统肌球蛋白那样得到深入研究，但已知或认为非传统肌球蛋白驱动许多形式的基于肌动蛋白的运动和细胞器运输。非传统肌球蛋白尾部存在信号结构域，如激酶结构域、SH3结构域、PH结构域或GTP酶激活结构域，这表明这些蛋白质也可以是信号转导途径的组成部分。由于肌球蛋白超家族的几个类别仅在低等真核生物或植物中发现（VIII、XI、XIII和XIV），在本综述中，我们将重点关注多细胞动物中发现的非传统肌球蛋白的结构和特性（不包括I类和V类，最近在其他地方已对其进行了综述）。将特别关注三类非传统肌球蛋白，它们在小鼠或人类中发生突变时可导致耳聋。此外，我们还讨论了一对有趣的结构域的发现，即肌球蛋白尾部同源性4（MyTH4）和FERM（带4.1、埃兹蛋白、根蛋白、膜突蛋白）结构域，它们存在于其他方面非常不同的肌球蛋白以及一种植物驱动蛋白样蛋白的尾部。还将总结新型非传统肌球蛋白鉴定方面的最新进展。
