Marsh J W, Taylor R K
Dartmouth Medical School, Department of Microbiology, Hanover, NH 03755, USA.
Mol Microbiol. 1998 Sep;29(6):1481-92. doi: 10.1046/j.1365-2958.1998.01031.x.
Cholera toxin secretion is dependent upon the extracellular protein secretion apparatus encoded by the eps gene locus of Vibrio cholerae. Although the eps gene locus encodes several type four prepilin-like proteins, the peptidase responsible for processing these proteins has not been identified. This report describes the identification of a prepilin peptidase from the V. cholerae genomic database by virtue of its homology with the PilD prepilin peptidase of Pseudomonas aeruginosa. Plasmid disruption or deletion of this peptidase gene in either EI Tor or classical V. cholerae O1 biotype strains results in a dramatic decrease in cholera toxin secretion. In the case of the EI Tor biotype mutants, surface expression of the type 4 pilus responsible for mannose-sensitive haemagglutination is abolished. The cloned V. cholerae peptidase processes either EpsI or MshA preproteins when co-expressed in E. coli. Mutation of the V. cholerae peptidase gene also results in a defect in virulence and decreased levels of OmpU. The V. cholerae peptidase gene sequence shows 80% homology with the Vibrio vulnificus VvpD type 4 prepilin peptidase required for pilus assembly and cytolysin secretion in V. vulnificus. Accordingly, the V. cholerae type 4 prepilin peptidase required for pilus assembly and cholera toxin secretion has been designated VcpD.
霍乱毒素的分泌依赖于霍乱弧菌eps基因座编码的细胞外蛋白质分泌装置。尽管eps基因座编码几种IV型前菌毛样蛋白，但负责加工这些蛋白的肽酶尚未被鉴定出来。本报告描述了通过与铜绿假单胞菌的PilD前菌毛肽酶的同源性，从霍乱弧菌基因组数据库中鉴定出一种前菌毛肽酶。在EI Tor或经典霍乱弧菌O1生物型菌株中，该肽酶基因的质粒破坏或缺失导致霍乱毒素分泌显著减少。对于EI Tor生物型突变体，负责甘露糖敏感血凝的IV型菌毛的表面表达被消除。当在大肠杆菌中共表达时，克隆的霍乱弧菌肽酶可加工EpsI或MshA前体蛋白。霍乱弧菌肽酶基因的突变也导致毒力缺陷和OmpU水平降低。霍乱弧菌肽酶基因序列与创伤弧菌中菌毛组装和溶细胞素分泌所需的创伤弧菌VvpD IV型前菌毛肽酶具有80%的同源性。因此，菌毛组装和霍乱毒素分泌所需的霍乱弧菌IV型前菌毛肽酶被命名为VcpD。
