Thermodynamic Signatures of the Antigen Binding Site of mAb 447-52D Targeting the Third Variable Region of HIV-1 gp120.Killikelly, A., Zhang, H.T., Spurrier, B., Williams, C., Gorny, M.K., Zolla-Pazner, S., Kong, X.P.
(2013) Biochemistry 52: 6249-6257
- PubMed: 23944979
- DOI: 10.1021/bi400645e
- PubMed Abstract:
The third variable region (V3) of HIV-1 gp120 plays a key role in viral entry into host cells; thus, it is a potential target for vaccine design. Human monoclonal antibody (mAb) 447-52D is one of the most broadly and potently neutralizing anti-V3 mAb ...
The third variable region (V3) of HIV-1 gp120 plays a key role in viral entry into host cells; thus, it is a potential target for vaccine design. Human monoclonal antibody (mAb) 447-52D is one of the most broadly and potently neutralizing anti-V3 mAbs. We further characterized the 447-52D epitope by determining a high-resolution crystal structure of the Fab fragment in complex with a cyclic V3 and interrogated the antigen-antibody interaction by a combination of site-specific mutagenesis, isothermal titration calorimetry (ITC) and neutralization assays. We found that 447-52D's neutralization capability is correlated with its binding affinity and at 25 °C the Gibbs free binding energy is composed of a large enthalpic component and a small favorable entropic component. The large enthalpic contribution is due to (i) an extensive hydrogen bond network, (ii) a π-cation sandwiching the V3 crown apex residue Arg(315), and (iii) a salt bridge between the 447-52D heavy chain residue Asp(H95) and Arg(315). Arg(315) is often harbored by clade B viruses; thus, our data explained why 447-52D preferentially neutralizes clade B viruses. Interrogation of the thermodynamic signatures of residues at the antigen binding interface gives key insights into their contributions in the antigen-antibody interaction.
Departments of Biochemistry and Molecular Pharmacology and ‡Department of Pathology, New York University School of Medicine , New York, New York 10016, United States.