Download MendeleyIsolation and structural characterization of a Zn2+-bound single-domain antibody against NorC, a putative multidrug efflux transporter in bacteria.
Kumar, S., Mahendran, I., Athreya, A., Ranjan, R., Penmatsa, A.(2020) J Biological Chem 295: 55-68
- PubMed: 31699895 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1074/jbc.RA119.010902
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Single-chain antibodies from camelids have served as powerful tools ranging from diagnostics and therapeutics to crystallization chaperones meant to study protein structure and function. In this study, we isolated a single-chain antibody from an Indian dromedary camel (ICab) immunized against a bacterial 14 TM helix transporter, NorC, from Staphylococcus aureus We identified this antibody in a yeast display screen built from mononuclear cells isolated from the immunized camel and purified the antibody from Escherichia coli after refolding it from inclusion bodies. The X-ray structure of the antibody at 2.15 Å resolution revealed a unique feature within its CDR3 loop, which harbors a Zn 2+ -binding site that substitutes for a loop-stabilizing disulfide bond. We performed mutagenesis to compromise the Zn 2+ -binding site and observed that this change severely hampered antibody stability and its ability to interact with the antigen. The lack of bound Zn 2+ also made the CDR3 loop highly flexible, as observed in all-atom simulations. Using confocal imaging of NorC-expressing E. coli spheroplasts, we found that the ICab interacts with the extracellular surface of NorC. This suggests that the ICab could be a valuable tool for detecting methicillin-resistant S. aureus strains that express efflux transporters such as NorC in hospital and community settings.
- Molecular Biophysics Unit, Indian Institute of Science, CV Raman Road, Bengaluru 560012, India.
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