Gli7 from R. cellulolyticum

[193]  Gude F., Molloy E. M., Horch T., Dell M., Dunbar K. L., Krabbe J., Groll M. and Hertweck C. 
A Specialized Polythioamide-Binding Protein Confers Antibiotic Self-Resistance in Anaerobic Bacteria
Angew. Chem. Int. Ed., 61 (e202206168), 1-9 PDF

Understanding antibiotic resistance mechanisms is central to the development of anti-infective therapies and genomics-based drug discovery. Yet, many knowledge gaps remain regarding the resistance strategies employed against novel types of antibiotics from less-explored producers such as anaerobic bacteria, among them the Clostridia. Through the use of genome editing and functional assays, we found that CtaZ confers self-resistance against the copper chelator and gyrase inhibitor closthioamide (CTA) in Ruminiclostridium cellulolyticum. Bioinformatics, biochemical analyses, and X-ray crystallography revealed CtaZ as a founding member of a new group of GyrI-like proteins. CtaZ is unique in binding a polythioamide scaffold in a ligand-optimized hydrophobic pocket, thereby confining CTA. By genome mining using CtaZ as a handle, we discovered previously overlooked homologs encoded by diverse members of the phylum Firmicutes, including many pathogens. In addition to characterizing both a new role for a GyrI-like domain in self-resistance and unprecedented thioamide binding, this work aids in uncovering related drug-resistance mechanisms.