Structural insights into the mechanism of single domain VHH antibody binding to cortisol

• Published in: FEBS letters Vol. 593; no. 11; pp. 1248 - 1256
• Main Authors: Ding, Lulu, Wang, Ziying, Zhong, Peiyu, Jiang, He, Zhao, Zhixuan, Zhang, Yiran, Ren, Zhen, Ding, Yu
• Format: Journal Article
• Language: English
• Published: England 01.06.2019
• Subjects: cortisol; nanobody; structure; VHH antibody; cortisol; VHH antibody; nanobody; structure
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1002/1873-3468.13398

To date, few structural models of VHH antibody binding to low molecular weight haptens have been reported. Here, we report the crystal structure of cortisol binding to its VHH antibody NbCor at pH 3.5 and 10.5. Cortisol binds to NbCor mainly by burying itself under the tunnel formed by the complementarity determining region 1 (CDR1) of NbCor. The affinity of NbCor binding to cortisol and similar compounds was also verified by a microscale thermophoresis assay. Combining our findings with several previously reported structures of hapten‐VHH antibody complexes, we propose that VHH antibodies exhibit a special mechanism of binding small haptens by encapsulating them in a tunnel formed by CDR1. Our findings provide useful structural information for the further development and optimization of hapten‐specific VHH antibodies. The high‐resolution crystal structure of VHH antibody NbCor–cortisol complex is solved. The binding mechanism is resolved via structural and thermodynamic analyses. Α binding model of small hapten to VHH antibody is proposed, which involves insertion of its hydrophobic portion into the complementarity determining region 1 tunnel.