Chemoproteomics with a Diaryliodonium Probe in Bacteria

The alarming increase in antimicrobial resistance (AMR) will soon limit treatment options for even routine infections, especially those caused by Gram-negative bacteria such as Acinetobacter baumannii. Here, we report a two-pronged approach to identify new vulnerabilities in such pathogens. Staring from diphenyleneiodonium (dPI) salts, which are compounds that have moderate antimicrobial activity against Gram-positive pathogens, we synthesized a focused heterocyclic library and report a new analogue that has much higher inhibitory potency against multidrug-resistant Acinetobacter baumannii and excellent efficacy in reduction of bacterial burden in a mouse neutropenic thigh infection model. The lead compound was also found to synergize with aminoglycosides, which are routinely used in the treatment of such infections in humans. Further, we synthesized an alkyne containing probe and using gel and mass spectrometry base chemoproteomics platforms, we identified proteins that have redox cofactors as putative targets for this class of compounds. Additionally, we also demonstrate that the modification of proteins is covalent and through a cysteine residue. Together, using complementary chemical biology approaches, new vulnerabilities in Gram-negative pathogens were identified that would help address a burgeoning global problem of AMR.