Natural products are important precursors for antibiotic drug design. These chemical scaffolds serve as syntheticinspiration for chemists who leverage their structures to develop novel antibacterials and chemical probes. We have previouslystudied carolacton, a natural product macrolactone from Sorangium cellulosum, and discovered a simplified derivative, A2, thatmaintained apparent biofilm inhibitory activity, although the biological target was unknown. Herein, we utilize affinity-based proteinprofiling (AfBPP) in situ during biofilm formation to identify the protein target using a photoexcitable cross-linking derivative of A2. From these studies, we identified glucan binding protein B (GbpB), a peptidoglycan hydrolase, as the primary target of A2. Furthercharacterization of the interaction between A2 and GbpB, as well as PcsB, a closely related homologue from the more pathogenic S.pneumoniae, revealed binding to the catalytic CHAP (cysteine, histidine, aminopeptidase) domain. To the best of our knowledge,this is the first report of a small-molecule binder of a conserved and essential bacterial CHAP hydrolase, revealing its potential as anantibiotic target. This work also highlights A2 as a useful tool compound for streptococci and as an initial scaffold for the design ofmore potent CHAP binders.

Scharnow, A. M., Solinski, A. E., Rowe, S., Drechsel, I., Zhang, H., Shaw, E., Page, J. E., Wu, H., Sieber, S. A., Wuest, W. M. "In Situ Biofilm Affinity-Based Protein Profiling Identifies the Streptococcal Hydrolase GbpB as the Target of a Carolacton-Inspired Chemical Probe" J. Am. Chem. Soc.

Link: https://doi.org/10.1021/jacs.4c06658

This reprint is licensed under CC-BY 4.0.