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首页> 外文期刊>Infection and immunity >Role of the C-Terminal Lysine Residues of Streptococcal Surface Enolase in Glu- and Lys-Plasminogen-Binding Activities of Group A Streptococci
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Role of the C-Terminal Lysine Residues of Streptococcal Surface Enolase in Glu- and Lys-Plasminogen-Binding Activities of Group A Streptococci

机译：链球菌表面烯醇化酶C末端赖氨酸残基在A组链球菌的Glu和Lys-纤溶酶结合活性中的作用

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Streptococcal surface enolase (SEN) is a major plasminogen-binding protein of group A streptococci. Our earlier biochemical studies have suggested that the region responsible for this property is likely located at the C-terminal end of the SEN molecule. In the present study, the gene encoding SEN was cloned from group A streptococci M6 isolate D471. A series of mutations in the sen gene corresponding to the C-terminal region (428KSFYNLKK435) of the SEN molecule were created by either deleting one or more terminal lysine residues or replacing them with leucine. All purified recombinant SEN proteins with altered C-terminal ends were found to be enzymatically active and were analyzed for their Glu- and Lys-plasminogen-binding activities. Wild-type SEN bound to Lys-plasminogen with almost three times more affinity than to Glu-plasminogen. However, the recombinant mutant SEN proteins with a deletion of Lys434-435 or with K435L and K434-435L replacements showed a significant decrease in Glu- and Lys-plasminogen-binding activities. Accordingly, a streptococcal mutant expressing SEN-K434-435L showed a significant decrease in Glu- and Lys-plasminogen-binding activities. Biochemical and functional analyses of the isogenic mutant strain revealed a significant decrease in its abilities to cleave a chromogenic tripeptide substrate, acquire plasminogen from human plasma, and penetrate the extracellular matrix. Together, these data indicate that the last two C-terminal lysine residues of surface-exposed SEN contribute significantly to the plasminogen-binding activity of intact group A streptococci and hence to their ability to exploit host properties to their own advantage in tissue invasion.
机译：链球菌表面烯醇化酶（SEN）是A组链球菌的主要纤溶酶原结合蛋白。我们较早的生化研究表明，负责此特性的区域可能位于SEN分子的C末端。在本研究中，从A组链球菌M6分离株D471中克隆了编码SEN的基因。通过删除任一序列，在SEN分子的C末端区域（ 428 KSFYNLKK 435 ）对应的 sen 基因中产生了一系列突变。一个或多个末端赖氨酸残基或将其替换为亮氨酸。发现具有改变的C-末端的所有纯化的重组SEN蛋白具有酶活性，并分析了它们的Glu-和Lys-纤溶酶原结合活性。野生型SEN与L​​ys-纤溶酶原的结合亲和力几乎是对Glu-纤溶酶原的三倍。但是，具有Lys434-435缺失或K435L和K434-435L替代的重组突变体SEN蛋白显示Glu和Lys-纤溶酶原结合活性显着降低。因此，表达SEN-K434-435L的链球菌突变体显示出Glu-和Lys-纤溶酶原结合活性显着降低。对等基因突变菌株的生化和功能分析表明，其裂解发色三肽底物，从人血浆中获取纤溶酶原并穿透细胞外基质的能力显着降低。总之，这些数据表明，表面暴露的SEN的最后两个C端赖氨酸残基对完整的A组链球菌的纤溶酶原结合活性有重要贡献，因此也发挥了它们利用宿主特性发挥其自身优势的能力，从而可以入侵组织。

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