Covalent inhibition by a natural product-inspired latent electrophile

Abstract

Strategies to target specific protein cysteines are critical to covalent probe and drug discovery. 3-bromo-4,5-dihy-droxazole is a natural product-inspired, synthetically accessible electrophilic moiety that has previously been shown to react with nucleophilic cysteines in the active site of purified enzymes. Here we define the global cysteine reactivity and selectivity of a set of 3-bromo-4,5-dihydroxazole-functionalized chemical fragments using competitive chemoproteomic profiling methods. Our study demonstrates that 3-bromo-4,5-dihydroxazoles capably engage reactive cysteine residues in the human proteome and the selectivity landscape of cysteines liganded by 3-bromo-4,5-dihydroxazoles is distinct from that of haloacetamide electrophiles. Given its tem-pered reactivity, 3-bromo-4,5-dihydroxazoles showed restricted, selective engagement with proteins driven by interactions between a tunable binding element and the complementary protein sites. We further validate that 3-bromo-4,5-dihydroxazoles form covalent conjugates with glutathione S-transferase Pi (GSTP1) and peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1), emerging anti-cancer targets. Together, this study expands the spectrum of optimizable chemical tools for covalent ligand discovery and high-lights the utility of 3-bromo-4,5-dihydroxazole as a cysteine-reactive electrophile. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=57 SRC="FIGDIR/small/524242v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@13b987eorg.highwire.dtl.DTLVardef@1987ae1org.highwire.dtl.DTLVardef@1ab4fb9org.highwire.dtl.DTLVardef@1ff1f71_HPS_FORMAT_FIGEXP M_FIG C_FIG