Goodson H V
Department of Biochemistry, Beckman Center for Molecular and Genetic Medicine, Stanford University Medical School, California 94305.
Soc Gen Physiol Ser. 1994;49:141-57.
We have used distance matrix and maximum parsimony methods to study the evolutionary relationships between members of the myosin superfamily of molecular motors. Amino acid sequences of the conserved core of the motor region were used in the analysis. Our results show that myosins can be divided into at least three main classes, with two types of unconventional myosin being no more related to each other than they are to conventional myosin. Myosins have traditionally been classified as conventional or unconventional, with many of the unconventional myosin proteins thought to be distributed in a narrow range of organisms. We find that members of all three of these main classes are likely to be present in most (or all) eukaryotes. Three proteins do not cluster within the three main groups and may each represent additional classes. The structure of the trees suggests that these ungrouped proteins and some of the subclasses of the main classes are also likely to be widely distributed, implying that most eukaryotic cells contain many different myosin proteins. The groupings derived from phylogenetic analysis of myosin head sequences agree strongly with those based on tail structure, developmental expression, and (where available) enzymology, suggesting that specific head sequences have been tightly coupled to specific tail sequences throughout evolution. Analysis of the relationships within each class has interesting implications. For example, smooth muscle myosin and striated muscle myosin seem to have independently evolved from nonmuscle myosin. Furthermore, brush border myosin I, a type of protein initially thought to be specific to specialized metazoan tissues, probably has relatives that are much more broadly distributed.
我们运用距离矩阵和最大简约法来研究分子马达肌球蛋白超家族成员之间的进化关系。分析中使用了马达区域保守核心的氨基酸序列。我们的结果表明，肌球蛋白可至少分为三大类，其中两类非常规肌球蛋白彼此之间的关联并不比它们与常规肌球蛋白的关联更为紧密。传统上，肌球蛋白被分为常规或非常规两类，许多非常规肌球蛋白蛋白被认为分布在范围狭窄的生物体中。我们发现，这三大类中的所有成员可能存在于大多数（或所有）真核生物中。有三种蛋白质未聚集在这三个主要组内，可能各自代表其他类别。树状结构表明，这些未分组的蛋白质以及主要类别的一些亚类也可能广泛分布，这意味着大多数真核细胞含有许多不同的肌球蛋白蛋白。基于肌球蛋白头部序列的系统发育分析得出的分组与基于尾部结构、发育表达以及（如有可用信息）酶学的分组高度一致，这表明在整个进化过程中，特定的头部序列与特定的尾部序列紧密相连。对每个类别内部关系的分析具有有趣的启示。例如，平滑肌肌球蛋白和横纹肌肌球蛋白似乎是从非肌肉肌球蛋白独立进化而来的。此外，最初被认为是特定后生动物组织特有的刷状缘肌球蛋白I，可能有分布更为广泛的亲属。
