Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8.
Proc Natl Acad Sci U S A. 2010 Aug 10;107(32):14384-9. doi: 10.1073/pnas.1005822107. Epub 2010 Jul 26.
Evolutionary relationships may exist among very diverse groups of proteins even though they perform different functions and display little sequence similarity. The tailed bacteriophages present a uniquely amenable system for identifying such groups because of their huge diversity yet conserved genome structures. In this work, we used structural, functional, and genomic context comparisons to conclude that the head-tail connector protein and tail tube protein of bacteriophage lambda diverged from a common ancestral protein. Further comparisons of tertiary and quaternary structures indicate that the baseplate hub and tail terminator proteins of bacteriophage may also be part of this same family. We propose that all of these proteins evolved from a single ancestral tail tube protein fold, and that gene duplication followed by differentiation led to the specialized roles of these proteins seen in bacteriophages today. Although this type of evolutionary mechanism has been proposed for other systems, our work provides an evolutionary mechanism for a group of proteins with different functions that bear no sequence similarity. Our data also indicate that the addition of a structural element at the N terminus of the lambda head-tail connector protein endows it with a distinctive protein interaction capability compared with many of its putative homologues.
即使蛋白质执行不同的功能并且显示出很少的序列相似性，它们之间也可能存在非常不同的蛋白质组之间的进化关系。长尾噬菌体提供了一个独特的系统来识别这些蛋白质组，因为它们具有巨大的多样性和保守的基因组结构。在这项工作中，我们使用结构、功能和基因组上下文比较得出结论，噬菌体 lambda 的头部-尾部连接器蛋白和尾部管蛋白是从一个共同的祖先蛋白分化而来的。对三级和四级结构的进一步比较表明，噬菌体的基板中心和尾部终止蛋白也可能是这个家族的一部分。我们提出，所有这些蛋白质都是从一个单一的祖先尾部管蛋白折叠进化而来的，基因复制后分化导致了这些蛋白质在今天的噬菌体中具有特殊的作用。尽管这种进化机制已经被提出用于其他系统，但我们的工作为一组具有不同功能且没有序列相似性的蛋白质提供了一种进化机制。我们的数据还表明，lambda 头部-尾部连接器蛋白 N 端添加一个结构元素，使其与许多假定的同源物相比，具有独特的蛋白质相互作用能力。
