Campylobacter fetus surface layer proteins are transported by a type I secretion system
Campylobacter fetus surface layer proteins are transported by a type I secretion system
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DOI：
10.1128/jb.180.24.6450-6458.1998
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发表时间：
1998-12-01
影响因子：
3.2
通讯作者：
Blaser, MJ
中科院分区：
文献类型：
--
作者：
Thompson, SA;Shedd, OL;Blaser, MJ
胎儿弯曲杆菌（Campylobacter fetus）是有蹄类动物和人类的细菌病原体，其毒力部分由赋予血清抗性的次晶表面层（S-层）的存在介导。S-层的亚基是S-层蛋白（SLP），其在缺乏N-末端信号序列的情况下分泌并附着于A型或B C型。胎儿脂多糖以血清特异性方式，A型菌株23 D的多个SLP（由sapA同源物编码）的抗原性变异通过侧翼为两个sapA同源物的含启动子的DNA元件的倒位发生。克隆并测序了C. fetus 23 D揭示了可能的5.6-kb操纵子，该操纵子由四个重叠基因（sapCDEF，大小分别为1，035、1，752、1，284和1，302 bp）组成，以与sapA相反的方向转录。这四个基因也存在于B型菌株84-107的可逆区中，并且实际上与A型菌株中的对应物相同。尽管SapC没有数据库同源性，但SapD、SapE和SapF预测了与I型蛋白质分泌系统（以大肠杆菌HlyBD/TolC或欧文氏菌PrtDEF为代表）的氨基酸同源性，所述I型蛋白质分泌系统利用C末端分泌信号来介导来自其他细菌物种的溶血素、白细胞毒素或蛋白酶的分泌。分析了四种C.胎儿SLP揭示了作为潜在分泌信号的保守结构。梭胎儿sapD突变体既不产生也不分泌SLP，E. coli表达C.胎儿sapA和sapCDEF分泌SapA，表明sapCDEF基因足以分泌SLP，C.因此，胎儿SLP通过I型分泌系统转运到细胞表面。
The virulence of Campylobacter fetus, a bacterial pathogen of ungulates and humans, is mediated in part by the presence of a paracrystalline surface layer (S-layer) that confers serum resistance, The subunits of the S-layer are S-layer proteins (SLPs) that are secreted in the absence of an N-terminal signal sequence and attach to either type A or B C. fetus lipopolysaccharide in a serospecific manner, Antigenic variation of multiple SLPs (encoded by sapA homologs) of type A strain 23D occurs by inversion of a promoter-containing DNA element flanked by two sapA homologs. Cloning and sequencing of the entire 6.2-kb invertible region from C. fetus 23D revealed a probable 5.6-kb operon of four overlapping genes (sapCDEF, with sizes of 1,035, 1,752, 1,284, and 1,302 bp, respectively) transcribed in the opposite direction from sapA. The four genes also were present in the invertible region of type B strain 84-107 and were virtually identical to their counterparts in the type A strain. Although SapC had no database homologies, SapD, SapE, and SapF had predicted amino acid homologies with type I protein secretion systems (typified by Escherichia coli HlyBD/TolC or Erwinia chrysanthemi PrtDEF) that utilize C-terminal secretion signals to mediate the secretion of hemolysins, leukotoxins, or proteases from other bacterial species. Analysis of the C termini of four C. fetus SLPs revealed conserved structures that are potential secretion signals. A C. fetus sapD mutant neither produced nor secreted SLPs, E. coli expressing C. fetus sapA and sapCDEF secreted SapA, indicating that the sapCDEF genes are sufficient for SLP secretion, C. fetus SLPs therefore are transported to the cell surface by a type I secretion system.