Thiol-based chemical probes exhibit antiviral activity against SARS-CoV-2 via allosteric disulfide disruption in the spike glycoprotein

Abstract

Significance Some coronaviruses utilize angiotensin-converting enzyme 2 (ACE2) for entry into host cells. Although reducing agents, such as N -acetylcysteine, disrupt viral binding to ACE2 in general, these compounds are cytotoxic, have low potency, and because of their membrane permeability, have undefined mechanism of action. With qualitative chemoproteomic mapping to delineate cysteine thiol/disulfide reactivity in native spike and recombinant receptor binding domain (RBD), we report nontoxic, cell-impermeable thiol-based chemical probes that significantly decrease the ACE2 binding and infectivity of SARS-CoV-2. We map the reactive cysteines and show the dynamic consequences of breaking allosteric disulfide bonds in the RBD. Altogether, our work underscores a clear redox-based mechanism of antiviral activity in which reducing compounds disrupt key RBD disulfides specifically in extracellular spaces.