An anomalous type IV secretion system in Rickettsia is evolutionarily conserved.
An anomalous type IV secretion system in Rickettsia is evolutionarily conserved.
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DOI：
10.1371/journal.pone.0004833
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发表时间：
2009
期刊：
影响因子：
3.7
通讯作者：
Azad AF
中科院分区：
文献类型：
--
作者：
Gillespie JJ;Ammerman NC;Dreher-Lesnick SM;Rahman MS;Worley MJ;Setubal JC;Sobral BS;Azad AF
细菌IV型分泌系统（t4ss）包括多种转运蛋白家族，其功能包括偶联、能力和效应分子（DNA和/或蛋白质）易位。立克次体是广泛真核生物的细胞内共生体/病原体，来自立克次体的13个基因组序列显示，相对于农杆菌原型（vir），立克次体的T4SS降低。然而，立克次体T4SS在共生/毒力中的作用尚未被功能表征，其底物也不为人所知。T4SS结构/功能信息与先前鉴定的立克次体成分的叠加意味着功能性立克次体T4SS。virB4， virB8和virB9是重复的，但每个拷贝只有一个具有其他t4ss中相似基因的保守特征。一个异常复制的VirB6基因编码了5个疏水蛋白，这些蛋白只在已知的短区域内保守，参与了肿瘤杆菌的DNA转移。virB1， virB2和virB7是新发现的，揭示了相对于vir原型只缺乏virB5的立克次体T4SS。系统发育估计表明，尽管基因重排成一个由五个小岛组成的群岛，但所有成分都是垂直遗传的。立克次体VirB7/VirB9与ε-变形细菌的ComB7/ComB9蛋白的相似性，以及与军团菌lvh T4SS的系统发育亲缘关系，表明立克次体的祖先可能是在居住在原生动物宿主体内时，从远亲细菌那里获得了类似病毒的位点。这些系统的现代修改可能反映了各种真核宿主细胞的多样化。我们提出了rvh（立克次体同源物）T4SS，一种进化保守的转运蛋白，在立克次体生物学中具有未知的作用。这项工作为未来该系统的实验室表征奠定了基础，也确定了军团菌lvh T4SS是一个合适的遗传模型。
Bacterial type IV secretion systems (T4SSs) comprise a diverse transporter family functioning in conjugation, competence, and effector molecule (DNA and/or protein) translocation. Thirteen genome sequences from Rickettsia, obligate intracellular symbionts/pathogens of a wide range of eukaryotes, have revealed a reduced T4SS relative to the Agrobacterium tumefaciens archetype (vir). However, the Rickettsia T4SS has not been functionally characterized for its role in symbiosis/virulence, and none of its substrates are known. Superimposition of T4SS structural/functional information over previously identified Rickettsia components implicate a functional Rickettsia T4SS. virB4, virB8 and virB9 are duplicated, yet only one copy of each has the conserved features of similar genes in other T4SSs. An extraordinarily duplicated VirB6 gene encodes five hydrophobic proteins conserved only in a short region known to be involved in DNA transfer in A. tumefaciens. virB1, virB2 and virB7 are newly identified, revealing a Rickettsia T4SS lacking only virB5 relative to the vir archetype. Phylogeny estimation suggests vertical inheritance of all components, despite gene rearrangements into an archipelago of five islets. Similarities of Rickettsia VirB7/VirB9 to ComB7/ComB9 proteins of ε-proteobacteria, as well as phylogenetic affinities to the Legionella lvh T4SS, imply the Rickettsiales ancestor acquired a vir-like locus from distantly related bacteria, perhaps while residing in a protozoan host. Modern modifications of these systems likely reflect diversification with various eukaryotic host cells. We present the rvh (Rickettsiales vir homolog) T4SS, an evolutionary conserved transporter with an unknown role in rickettsial biology. This work lays the foundation for future laboratory characterization of this system, and also identifies the Legionella lvh T4SS as a suitable genetic model.
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影响因子：
6.7
作者：
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通讯作者：
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作者：
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