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首页> 外文期刊>Infection and immunity >Replacement of Histidine 340 with Alanine Inactivates the Group A Streptococcus Extracellular Cysteine Protease Virulence Factor
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Replacement of Histidine 340 with Alanine Inactivates the Group A Streptococcus Extracellular Cysteine Protease Virulence Factor

机译：用丙氨酸替代组氨酸340可灭活A组链球菌胞外半胱氨酸蛋白酶致病因子

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摘要

Streptococcus pyogenes expresses a highly conserved extracellular cysteine protease that is a virulence factor for invasive disease, including soft tissue infection. Site-directed mutagenesis was used to generate a His340Ala recombinant mutant protein that was made as a stable 40-kDa zymogen by Escherichia coli. Purified His340Ala protein was proteolytically inactive when bovine casein and human fibronectin were used as substrates. Wild-type 28-kDa streptococcal protease purified from S. pyogenes processed the 40-kDa mutant zymogen to a 28-kDa mature form, a result suggesting that the derivative protein retained structural integrity. The data are consistent with the hypothesis that His340 is an enzyme active site residue, an idea confirmed by recent solution of the zymogen crystal structure (T. F. Kagawa, J. C. Cooney, H. M. Baker, S. McSweeney, M. Liu, S. Gubba, J. M. Musser, and E. N. Baker, Proc. Natl. Acad. Sci. USA 97:2235–2240, 2000). The data provide additional insight into structure-function relationships in thisS. pyogenes virulence factor.
机译：化脓性链球菌表达高度保守的细胞外半胱氨酸蛋白酶，其是包括软组织感染在内的侵袭性疾病的致病因子。定点诱变用于产生His340Ala重组突变蛋白，该蛋白被大肠杆菌制成稳定的40 kDa酶原。当使用牛酪蛋白和人纤连蛋白作为底物时，纯化的His340Ala蛋白没有蛋白水解活性。从化脓性链球菌纯化的野生型28 kDa链球菌蛋白酶将40 kDa的突变酶原加工成28 kDa的成熟形式，结果表明衍生蛋白保留了结构完整性。数据与His340是酶活性位点残基的假设相符，这一观点已被酶原晶体结构的最新解决方案所证实（TF Kagawa，JC Cooney，HM Baker，S.McSweeney，M.Liu，S.Gubba，JM Musser和EN Baker，美国国家科学院院刊97：2235-2240，2000年）。数据提供了对此结构与功能关系的更多了解。化脓性毒力因子。

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