Members of the CA class of cysteine proteases have multifaceted roles in physiology and virulence for many bacteria. Streptococcal pyrogenic exotoxin B (SpeB) is secreted by Streptococcus pyogenes and implicated in the pathogenesis of the bacterium through degradation of key human immune effector proteins. Here, we developed and characterized a clickable inhibitor, 2S-alkyne, based on X-ray crystallographic analysis and structure–activity relationships. Our SpeB probe showed irreversible enzyme inhibition in biochemical assays and labeled endogenous SpeB in cultured S. pyogenes supernatants. Importantly, application of 2S-alkyne decreased S. pyogenes survival in the presence of human neutrophils and supports the role of SpeB-mediated proteolysis as a mechanism to limit complement-mediated host defense. We posit that our SpeB inhibitor will be a useful chemical tool to regulate, label, and quantitate secreted cysteine proteases with SpeB-like activity in complex biological samples and a lead candidate for new therapeutics designed to sensitize S. pyogenes to host immune clearance.

中文翻译：

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不可逆抑制剂，以探索化脓性链球菌半胱氨酸蛋白酶SpeB在逃避宿主补体防御中的作用。

CA类半胱氨酸蛋白酶的成员在许多细菌的生理和毒力中具有多方面的作用。链球菌热原性外毒素B（SpeB）由化脓性链球菌分泌，并通过降解关键的人类免疫效应蛋白而参与细菌的发病机理。在这里，我们基于X射线晶体学分析和结构-活性关系开发了可点击的抑制剂2 S-炔烃并对其进行了表征。我们的SpeB探针在生化分析中显示出不可逆的酶抑制作用，并在培养的化脓性链球菌上清液中标记了内源性SpeB 。重要的是，使用2 S-炔烃可减少化脓性链球菌在人类嗜中性粒细胞的存在下存活并支持SpeB介导的蛋白水解作为限制补体介导的宿主防御的机制的作用。我们认为，我们的SpeB抑制剂将是一种有用的化学工具，可调节，标记和定量在复杂的生物样品中具有SpeB样活性的分泌的半胱氨酸蛋白酶，并且是旨在使化脓性链球菌对宿主免疫清除敏感的新疗法的主要候选药物。