链球菌烯醇化酶与致热外毒素B成熟的相关性

在化脓性链球菌致热外毒素B(SpeB)活性阳性菌株对数生长末期的细胞培养液中发现1个分子量约为50000的蛋白, 该蛋白随后消失; 用聚丙烯酰胺凝胶电泳(SDS-PAGE)分离, 串联质谱(MS/MS)分析确认该蛋白为链球菌烯醇化酶(Enolase, Eno); 通过基因敲除方法构建eno基因缺失突变株, 研究了Eno蛋白对SpeB活性形成的影响. 结果表明, eno基因的缺失推迟SpeB成熟的时间; 通过Far-Western blot 分析显示, Eno与SpeB之间能发生相互作用. 考虑到化脓性链球菌胞外蛋白通过同一通道分泌, 推测Eno可能参与了SpeB酶原分泌到胞外的过程, 为新发现的SpeB蛋白分子伴侣.

Correlation of Enolase and the Maturation of SpeB in Streptococcus pyogenes

Group A Streptococci(GAS) is an important Gram-positive human pathogen, which causes mild to severe diseases. The ability of GAS to cause infection is associated with the production of an array of secreted and cell-wall associated virulence factors. One key secreted virulence factor is a cysteine protease called streptococcal pyrogenic exotoxin B(SpeB). This protein is initially secreted as a 40000 precursor zymogen, and is subsequently cleaved to a 28000 mature form. The conversion of the zymogen form of SpeB is extremely complex and unclear. In this paper we reported a protein involved in the maturation of SpeB in the supernatant of Group A Streptococci. This protein was the streptococcus host plasminogen receptor, enolase(Eno) identified by MS/MS analysis. We constructed the eno in-deletion mutants by the method of gene knock out and investigated the correlation of enolase and maturation of SpeB in GAS. Western blot analysis and protease assays revealed a delay in the maturation of SpeB in supernatant of the eno in-deletion mutants comparing with the wild type strains. Far-Western blot analysis showed that SpeB can bind to Eno, which interact with each other. These data imply that the function of Eno, as like HtrA and RopA, is a chaperone, the regulation of protease activity and the mechanism of secretion in GAS.