Foth Bernardo J, Goedecke Marc C, Soldati Dominique
Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, 1 Rue Michel-Servet, 1211 Geneva, Switzerland.
Proc Natl Acad Sci U S A. 2006 Mar 7;103(10):3681-6. doi: 10.1073/pnas.0506307103. Epub 2006 Feb 27.
Myosins are eukaryotic actin-dependent molecular motors important for a broad range of functions like muscle contraction, vision, hearing, cell motility, and host cell invasion of apicomplexan parasites. Myosin heavy chains consist of distinct head, neck, and tail domains and have previously been categorized into 18 different classes based on phylogenetic analysis of their conserved heads. Here we describe a comprehensive phylogenetic examination of many previously unclassified myosins, with particular emphasis on sequences from apicomplexan and other chromalveolate protists including the model organism Toxoplasma, the malaria parasite Plasmodium, and the ciliate Tetrahymena. Using different phylogenetic inference methods and taking protein domain architectures, specific amino acid polymorphisms, and organismal distribution into account, we demonstrate a hitherto unrecognized common origin for ciliate and apicomplexan class XIV myosins. Our data also suggest common origins for some apicomplexan myosins and class VI, for classes II and XVIII, for classes XII and XV, and for some microsporidian myosins and class V, thereby reconciling evolutionary history and myosin structure in several cases and corroborating the common coevolution of myosin head, neck, and tail domains. Six novel myosin classes are established to accommodate sequences from chordate metazoans (class XIX), insects (class XX), kinetoplastids (class XXI), and apicomplexans and diatom algae (classes XXII, XXIII, and XXIV). These myosin (sub)classes include sequences with protein domains (FYVE, WW, UBA, ATS1-like, and WD40) previously unknown to be associated with myosin motors. Regarding the apicomplexan "myosome," we significantly update class XIV classification, propose a systematic naming convention, and discuss possible functions in these parasites.
肌球蛋白是真核生物中依赖肌动蛋白的分子马达，对多种功能至关重要，如肌肉收缩、视觉、听觉、细胞运动以及顶复门寄生虫对宿主细胞的侵袭。肌球蛋白重链由不同的头部、颈部和尾部结构域组成，此前根据其保守头部的系统发育分析被分为18个不同的类别。在此，我们描述了对许多先前未分类的肌球蛋白进行的全面系统发育研究，特别关注来自顶复门和其他色素体藻类原生生物的序列，包括模式生物弓形虫、疟原虫以及纤毛虫四膜虫。使用不同的系统发育推断方法，并考虑蛋白质结构域结构、特定氨基酸多态性和生物分布，我们证明了纤毛虫和顶复门类十四肌球蛋白迄今未被认识到的共同起源。我们的数据还表明，一些顶复门肌球蛋白与类六肌球蛋白、类二和类十八肌球蛋白、类十二和类十五肌球蛋白以及一些微孢子虫肌球蛋白与类五肌球蛋白有共同起源，从而在几个案例中协调了进化历史和肌球蛋白结构，并证实了肌球蛋白头部、颈部和尾部结构域的共同协同进化。建立了六个新的肌球蛋白类别，以容纳来自脊索动物后生动物（类十九）、昆虫（类二十）、动质体（类二十一）以及顶复门和硅藻（类二十二、类二十三和类二十四）的序列。这些肌球蛋白（亚）类别包括具有先前未知与肌球蛋白马达相关的蛋白质结构域（FYVE、WW、UBA、ATS1样和WD40）的序列。关于顶复门的“肌小体”，我们显著更新了类十四分类，提出了系统的命名惯例，并讨论了这些寄生虫中可能的功能。
