Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.21.349639v1?rss=1 Authors: Kumar, S., Athreya, A., Gulati, A., Nair, R. M., Penmatsa, A. Abstract: Multi-drug efflux is a major mechanism of acquiring antimicrobial resistance among superbugs. In this study, we report the X-ray structure of NorC, a 14 transmembrane major facilitator superfamily member that is implicated in fluoroquinolone resistance in drug-resistant Staphylococcus aureus strains, at a resolution of 3.6 angstroms. The NorC structure was determined in complex with a single-domain camelid antibody that interacts at the extracellular face of the transporter and stabilizes it in an outward-open conformation. The complementarity determining regions of the antibody enter and block solvent access to the interior of the vestibule, thereby inhibiting alternating-access. NorC specifically interacts with an organic cation, tetraphenylphosphonium, although it does not demonstrate an ability to transport it. The interaction is compromised in the presence of NorC-antibody complex, consequently establishing a strategy to detect and block NorC and related efflux pumps through the use of single-domain camelid antibodies. Copy rights belong to original authors. Visit the link for more info