猪链球菌2型血清混浊因子基因的鉴定及其结构特征分析  

Identification and Structure Features of Opacity Factor Genes from Two Streptococcus suis 2 Strains Originated from China and Japan

作　　者：冯亚莉[1,2] 冉雪琴[1] 王嘉福[1] 钱龙[1] 

机构地区：[1]贵州大学动物科学学院,贵阳550025 [2]石药集团恩必普药业有限公司,石家庄052160

出　　处：《畜牧兽医学报》2012年第2期282-289,共8页ACTA VETERINARIA ET ZOOTECHNICA SINICA

基　　金：国家科技支撑计划(2008BADB5B02);贵州省科技创新人才团队建设专项(黔科合人才团队2009-4006);贵州省科学技术基金(黔科合J字(2006)2026号)

摘　　要：猪链球菌是猪的主要病原,也可导致人感染,其致病机理尚未明确。作者设计了1对特异性引物,采用特异性PCR从2株猪链球菌血清2型606中国分离株和607日本分离株的基因组中,分离出2种血清混浊因子(ofs)基因,全长3 016bp,编码938个氨基酸,其中日本分离株607的ofs基因序列与已知基因完全相同。中国分离株606的ofs基因与已知基因相差7个碱基,导致3个氨基酸替换,其中1个突变(Asp353Gly)位于蛋白的N端功能区,可能影响其血清混浊功能;另外2个氨基酸突变位于蛋白的C端重复区内。从2种OFS蛋白中,找出了细菌黏附因子共有的结构特征,2种OFS蛋白C端区含有保守的LPXTG结构,使OFS蛋白可固定于细菌的表面,但其中的3个重复序列与纤黏蛋白结合蛋白A等的相似性很低,两种OFS蛋白可能通过特殊的途径协助猪链球菌的黏附。猪链球菌ofs基因中重复序列和突变使得编码的蛋白表现出丰富的长度多态性。本研究获得的2种OFS属于中等长度的蛋白,均来自强毒力型猪链球菌。这些结果提示菌株606和607携带的ofs基因可能是猪链球菌的毒力基因,对猪链球菌的致病机理及其防治具有重要的意义。Streptococcus suis is a swine pathogen which causes serious inflammation of piglets. It can infect people in contact with diseased pig or its by-products. The mechanisms of S. suis path- ogenesis are poorly understood. Taking two S. suis serotype 2 strains 606 isolated from China and 607 from Japan as samples, opacity factor of S. suis （ors） genes were amplified from the ge- nomic DNA of these bacteria by PCR method. The ors genes contained 3 016 bp which encoded for 938 aa based on alignment analysis. The identity of nucleotide sequence of ofs gene from SS2 strain 607 was 100% to the reported SS2 genes while seven nucleotides in ofs of SS2 strain 606 were different and resulted in three amino acids substitution. One of the substitutions located at the N-terminal region of OFS protein in which glycin （without charge） was changed to be aspartic acid （with negative charge）. It was proposed that the change would have an effect on the OFS ability to opacify serum of mammals. The other two substitutions were found from the repeats in C-terminal region of OFS in SS2 strain 606. Furthermore, the length and amino acid constitute ofthree repeats in OFS of SS2 strain 606 and 607 was very divergent from that of fibronectin-binding protein A （FnBA） of Streptococcus dysgalactiae. It was suggested that the pathway of OFS pro- tein binding to fibronectin of host cells might be different from that of FnBA. However, OFS proteins did carry the typical structural elements of MSCRAMMs （microbial surface components recognizing adhesive matrix molecules） with a large N-terminal region, specific repeats and LPX- TG domain elements in the C-terminal region. It could be presumed that OFS of SS2 strain 606 and 607 function as an adhesin combined on the surface of bacteria and bind the fibronectin with its repeats at the C-terminus. The correlation between the OFS with moderate size （938 aa） and the high virulence of streptococci implied that ofs gene was a pivotal virulent gene of SS2 strain 606 and 607.

关 键 词：Ⅱ型猪链球菌 血清混浊因子 多态性 

分 类 号：S852.61[农业科学—基础兽医学]