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Contribution of asparagine residues to the stabilization of a proteinaceous antigen-antibody complex, HyHEL-10-hen egg white lysozyme.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2010 Mar 05; Vol. 285 (10), pp. 7686-96. Date of Electronic Publication: 2009 Dec 28. - Publication Year :
- 2010
-
Abstract
- Many germ line antibodies have asparagine residues at specific sites to achieve specific antigen recognition. To study the role of asparagine residues in the stabilization of antigen-antibody complexes, we examined the interaction between hen egg white lysozyme (HEL) and the corresponding HyHEL-10 variable domain fragment (Fv). We introduced Ala and Asp substitutions into the Fv side chains of L-Asn-31, L-Asn-32, and L-Asn-92, which interact directly with residues in HEL via hydrogen bonding in the wild-type Fv-HEL complex, and we investigated the interactions between these mutant antibodies and HEL. Isothermal titration calorimetric analysis showed that all the mutations decreased the negative enthalpy change and decreased the association constants of the interaction. Structural analyses showed that the effects of the mutations on the structure of the complex could be compensated for by conformational changes and/or by gains in other interactions. Consequently, the contribution of two hydrogen bonds was minor, and their abolition by mutation resulted in only a slight decrease in the affinity of the antibody for its antigen. By comparison, the other two hydrogen bonds buried at the interfacial area had large enthalpic advantage, despite entropic loss that was perhaps due to stiffening of the interface by the bonds, and were crucial to the strength of the interaction. Deletion of these strong hydrogen bonds could not be compensated for by other structural changes. Our results suggest that asparagine can provide the two functional groups for strong hydrogen bond formation, and their contribution to the antigen-antibody interaction can be attributed to their limited flexibility and accessibility at the complex interface.
- Subjects :
- Animals
Asparagine
Chickens
Crystallography, X-Ray
Hydrogen Bonding
Immunoglobulin Fragments genetics
Immunoglobulin Variable Region genetics
Models, Molecular
Molecular Structure
Muramidase antagonists & inhibitors
Muramidase genetics
Mutagenesis, Site-Directed
Thermodynamics
Antigen-Antibody Complex chemistry
Immunoglobulin Fragments chemistry
Immunoglobulin Variable Region chemistry
Muramidase chemistry
Protein Conformation
Subjects
Details
- Language :
- English
- ISSN :
- 1083-351X
- Volume :
- 285
- Issue :
- 10
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 20038580
- Full Text :
- https://doi.org/10.1074/jbc.M109.089623