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Differences in electrostatic properties at antibody-antigen binding sites: implications for specificity and
Neeti Sinha1, Srinivasan Mohan, Claudia A Lipschultz
1Basic Research Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Bldg. 469, Frederick, MD 21702, USA.
Biophysical Journal
|December 24, 2002
Summary
Antibody binding specificity is determined by electrostatic interactions. Higher electrostatics and strong salt bridges lead to greater specificity, while hydrophobic interactions promote cross-reactivity.
Area of Science:
- Protein-protein interactions
- Immunology
- Structural biology
Background:
- Antibodies HyHEL8, HyHEL10, and HyHEL26 recognize similar epitopes on hen egg-white lysozyme (HEL) with varying specificities.
- HH8 is most cross-reactive, HH26 is most sensitive, and HH10 is intermediate.
Purpose of the Study:
- Investigate intra- and intermolecular interactions in three antibody-protein complexes (HH8-HEL, HH26-HEL, HH10-HEL).
- Determine the role of electrostatic and hydrophobic interactions in antibody binding specificity and cross-reactivity.
Main Methods:
- Theoretical modeling of HH8-HEL and HH26-HEL complexes.
- X-ray crystallography of the HH10-HEL complex.
- Mutant modeling and surface plasmon resonance (SPR) studies.
Main Results:
- HH26-HEL exhibits the highest number of hydrogen bonds and salt bridges, including a stabilizing pentad network.
- HH8-HEL shows the lowest number of interactions, with hydrophobic contributions dominating binding energy.
- Electrostatic interactions, particularly strong and networked salt bridges, correlate with higher binding specificity.
Conclusions:
- Higher electrostatics, including short-range interactions and strong salt bridges, enhance antibody binding specificity.
- Hydrophobic-driven binding and fewer electrostatic interactions are linked to conformational flexibility and cross-reactivity.
- The study elucidates how variations in electrostatic interactions dictate antibody specificity and cross-reactivity.