Baseplate assembly of phage Mu: Defining the conserved core components of contractile-tailed phages and related bacterial systems
Baseplate assembly of phage Mu: Defining the conserved core components of contractile-tailed phages and related bacterial systems
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DOI：
10.1073/pnas.1607966113
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发表时间：
2016-09-06
影响因子：
11.1
通讯作者：
Davidson, Alan R.
中科院分区：
文献类型：
--
作者：
Buttner, Carina R.;Wu, Yingzhou;Davidson, Alan R.
可收缩的噬菌体尾巴是一种强大的穿透细胞的纳米机器，细菌利用这种机器来防御细菌和真核细胞。噬菌体T4的尾巴长期以来一直被用作理解可收缩的尾巴系统的范例，尽管与其他有收缩尾巴的噬菌体相比，T4的尾巴更复杂。在这里，我们提出了一个“简单的”收缩尾巴噬菌体基板组装的详细调查，即大肠杆菌噬菌体Mu。通过共表达各种可能的Mu基板蛋白组合，我们定义了该基板所需的成分，并描绘了其组装途径。我们表明，Mu底板是通过围绕中央枢纽复合体组织的楔形部件的独立组装而构建的。Mu楔体只由三个蛋白质亚基组成，而不是T4中同等结构中的七个蛋白质亚基。通过广泛的生物信息学分析，我们发现在大多数收缩尾巴噬菌体和前驱噬菌体中都可以鉴定出Mu基板基本成分的同源物。没有鉴定出类似T4的预言体。在可收缩的尾部衍生的细菌器官中也发现了保守的简单基板成分，如VI型分泌系统、Photorhabdus毒力盒和R型taroocins。我们的工作突出了噬菌体Mu楔形元件与VI型分泌系统的TssF和TSSG蛋白在进化行为上的联系和相似之处。此外，我们论证了Mu基板作为理解细菌噬菌体尾部衍生系统的模型系统的重要性。
Contractile phage tails are powerful cell puncturing nanomachines that have been co-opted by bacteria for self-defense against both bacteria and eukaryotic cells. The tail of phage T4 has long served as the paradigm for understanding contractile tail-like systems despite its greater complexity compared with other contractile-tailed phages. Here, we present a detailed investigation of the assembly of a "simple" contractile-tailed phage baseplate, that of Escherichia coli phage Mu. By coexpressing various combinations of putative Mu baseplate proteins, we defined the required components of this baseplate and delineated its assembly pathway. We show that the Mu baseplate is constructed through the independent assembly of wedges that are organized around a central hub complex. The Mu wedges are comprised of only three protein subunits rather than the seven found in the equivalent structure in T4. Through extensive bioinformatic analyses, we found that homologs of the essential components of the Mu baseplate can be identified in the majority of contractile-tailed phages and prophages. No T4-like prophages were identified. The conserved simple baseplate components were also found in contractile tail-derived bacterial apparatuses, such as type VI secretion systems, Photorhabdus virulence cassettes, and R-type tailocins. Our work highlights the evolutionary connections and similarities in the biochemical behavior of phage Mu wedge components and the TssF and TssG proteins of the type VI secretion system. In addition, we demonstrate the importance of the Mu baseplate as a model system for understanding bacterial phage tail-derived systems.