TolC-Dependent Secretion of an Ankyrin Repeat-Containing Protein of Rickettsia typhi
TolC-Dependent Secretion of an Ankyrin Repeat-Containing Protein of Rickettsia typhi
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DOI：
10.1128/jb.00793-12
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发表时间：
2012-09-01
影响因子：
3.2
通讯作者：
Azad, Abdu F.
中科院分区：
文献类型：
--
作者：
Kaur, Simran J.;Rahman, M. Sayeedur;Azad, Abdu F.
斑疹伤寒立克次体是鼠伤寒的病原体，是一种专性细胞内病原体，其生命周期涉及脊椎动物和无脊椎动物宿主。在本研究中，我们鉴定了一个基因（RT 0218），该基因编码一个C-末端含锚蛋白重复结构域的蛋白，命名为立克次体锚蛋白重复蛋白1（RARP-1），并将其鉴定为立克次体分泌的效应蛋白。伤寒。RT 0218在R.伤寒杆菌细胞内生长RARP-1由R.伤寒杆菌在哺乳动物细胞的体外感染过程中进入宿主细胞质。转录分析显示，RT 0218与相邻基因RT 0217（假设蛋白）和RT 0216（TolC）共转录为单个多顺反子mRNA。考虑到其在一些革兰氏阴性细菌病原体中作为细胞外蛋白分泌促进剂的功能之一，我们测试了TolC在RARP-1分泌中的可能作用。使用大肠杆菌C600和同基因tolC插入突变体作为替代宿主，我们的数据表明，RARP-1是分泌的TolC依赖的方式。缺失N端信号肽或C端锚蛋白重复序列可抑制野生型大肠杆菌的RARP-1分泌。杆菌重要的是，R.伤寒沙门氏菌tolC在E. colitolC突变体恢复了RARP-1的分泌，表明TolC在RARP-1跨外膜转运中起作用。这项工作表明，TolC组分的推定1型分泌系统的R。伤寒参与RARP-1的分泌过程。
Rickettsia typhi, the causative agent of murine (endemic) typhus, is an obligate intracellular pathogen with a life cycle involving both vertebrate and invertebrate hosts. In this study, we characterized a gene (RT0218) encoding a C-terminal ankyrin repeat domain-containing protein, named Rickettsia ankyrin repeat protein 1 (RARP-1), and identified it as a secreted effector protein of R. typhi. RT0218 showed differential transcript abundance at various phases of R. typhi intracellular growth. RARP-1 was secreted by R. typhi into the host cytoplasm during in vitro infection of mammalian cells. Transcriptional analysis revealed that RT0218 was cotranscribed with adjacent genes RT0217 (hypothetical protein) and RT0216 (TolC) as a single polycistronic mRNA. Given one of its functions as a facilitator of extracellular protein secretion in some Gram-negative bacterial pathogens, we tested the possible role of TolC in the secretion of RARP-1. Using Escherichia coli C600 and an isogenic tolC insertion mutant as surrogate hosts, our data demonstrate that RARP-1 is secreted in a TolC-dependent manner. Deletion of either the N-terminal signal peptide or the C-terminal ankyrin repeats abolished RARP-1 secretion by wild-type E. coli. Importantly, expression of R. typhi tolC in the E. coli tolC mutant restored the secretion of RARP-1, suggesting that TolC has a role in RARP-1 translocation across the outer membrane. This work implies that the TolC component of the putative type 1 secretion system of R. typhi is involved in the secretion process of RARP-1.