Biophysical Society Thematic Meeting | Stockholm 2022

Physical and Quantitative Approaches to Overcome Antibiotic Resistance

Poster Abstracts

24-POS Board 24 STRUCTURAL BASIS FOR INHIBITION OF THE DRUG EFFLUX PUMP NORA FROM STAPHYLOCOCCUS AUREUS Douglas Brawley 1 ; David B. Sauer 1,8 ; Shohei Koide 4,5 ; Victor Torres 3,6 ; Da-Neng Wang 1,7 ; Nathaniel Traaseth 2 ; 1 New York University School of Medicine, Skirball Institute of Biomolecular Medicine, New York, NY, USA 2 New York University, Department of Chemistry, New York, NY, USA 3 New York University School of Medicine, Department of Microbiology, New York, NY, USA 4 New York University School of Medicine, Perlmutter Cancer Center, New York, NY, USA 5 New York University School of Medicine, Department of Biochemistry and Molecular Pharmacology, New York, NY, USA 6 New York University School of Medicine, Antimicrobial-Resistant Pathogens Program, New York, NY, USA 7 New York University School of Medicine, Department of Cell Biology, New York, NY, USA 8 University of Oxford, Centre for Medicines Discovery, Oxford, United Kingdom Membrane protein efflux pumps confer antibiotic resistance by extruding structurally distinct compounds and lowering their intracellular concentration. Yet, there are no clinically approved drugs to inhibit efflux pumps, which would potentiate the effi- cacy of existing antibiotics rendered ineffective by drug efflux. Here, we identified synthetic antigen-binding (Fab) fragments that inhibit the quinolone transporter NorA from methicillin-resistant Staphylococcus aureus (MRSA). Structures of two NorA– Fab complexes determined using cryo-electron microscopy (cryo-EM) reveal a Fab loop deeply inserted in the substrate-binding pocket of NorA. An arginine residue on this loop interacts with two neighboring aspartate and glutamate residues essential for NorA-mediated antibiotic resistance in MRSA. Peptide mimics of the Fab loop inhibit NorA with submicromolar potency and ablate MRSA growth in combination with the antibiotic norfloxacin. These findings establish a class of peptide inhibitors that block antibiotic efflux in MRSA by targeting indispensable residues in NorA without the need for membrane permeability.

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