Jordan L. Woehl, Seiya Kitamura, Nicholas Dillon, Zhen Han, Landon J. Edgar, Victor Nizet, and Dennis W. Wolan
ACS Chemical Biology 2020
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 develop and characterize 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.
