Burrows L L, Lo R Y
Department of Microbiology, University of Guelph, Ontario, Canada.
Infect Immun. 1992 Jun;60(6):2166-73. doi: 10.1128/iai.60.6.2166-2173.1992.
RTX cytolysins are a family of calcium-dependent, pore-forming, secreted toxins found in a variety of gram-negative bacteria. The prototypical member of this family is the alpha-hemolysin of Escherichia coli. The RTX genetic determinants from seven members of the family Pasteurellaceae, Pasteurella haemolytica, Actinobacillus actinomycetemcomitans, and A. pleuropneumoniae serotypes 1,5,7, and 9 were previously cloned and sequenced. Using the leukotoxin determinant from P. haemolytica serotype A1 as a probe, we detected the presence of RTX-type determinants in Actinobacillus suis, A. equuli, and A. lignieresii of the family Pasteurellaceae. All three species elaborate proteins of approximately 104 to 110 kDa that are recognized by polyclonal antisera against the 104-kDa hemolysin of A. pleuropneumoniae serotype 1. An RTX determinant of A. suis isolate 3714 was cloned and sequenced and was found to be almost identical to the RTX determinant of A. pleuropneumoniae serotypes 5 and 9. In addition, the determinant is not composed of four contiguous genes, as had been reported for most other RTX determinants; instead, the genes encoding the two proteins responsible for secretion of the toxin are at a locus distinct from that containing the toxin structural and activation genes.
RTX溶细胞素是一类钙依赖性、形成孔道的分泌型毒素，存在于多种革兰氏阴性细菌中。该家族的典型成员是大肠杆菌的α-溶血素。此前已克隆并测序了巴斯德氏菌科7个成员（溶血巴斯德氏菌、伴放线放线杆菌以及胸膜肺炎放线杆菌血清型1、5、7和9）的RTX遗传决定簇。以溶血巴斯德氏菌A1血清型的白细胞毒素决定簇为探针，我们在巴斯德氏菌科的猪放线杆菌、马驹放线杆菌和里氏放线杆菌中检测到了RTX型决定簇的存在。所有这三个物种都能产生大约104至110 kDa的蛋白质，这些蛋白质可被针对胸膜肺炎放线杆菌血清型1的104 kDa溶血素的多克隆抗血清识别。克隆并测序了猪放线杆菌分离株3714的一个RTX决定簇，发现它与胸膜肺炎放线杆菌血清型5和9的RTX决定簇几乎相同。此外，该决定簇并非由四个相邻基因组成，而大多数其他RTX决定簇此前曾有此报道；相反，编码负责毒素分泌的两种蛋白质的基因位于一个与包含毒素结构和激活基因的位点不同的位置。
