The role of hydrogen bonding via interfacial water molecules in antigen-antibody complexation. The HyHEL-10-HEL interaction.
To study the role of hydrogen bonding via interfacial water molecules in protein-protein interactions, we examined the interaction between hen egg white lysozyme (HEL) and its HyHEL-10 variable domain fragment (Fv) antibody. We constructed three antibody mutants (l-Y50F, l-S91A, and l-S93A) and investigated the interactions between the mutant Fvs and HEL. Isothermal titration calorimetry indicated that the mutations significantly decreased the negative enthalpy change (8-25 kJ mol(-1)), despite some offset by a favorable entropy change. X-ray crystallography demonstrated that the complexes had nearly identical structures, including the positions of the interfacial water molecules. Taken together, the isothermal titration calorimetric and x-ray crystallographic results indicate that hydrogen bonding via interfacial water enthalpically contributes to the Fv-HEL interaction despite the partial offset because of entropy loss, suggesting that hydrogen bonding stiffens the antigen-antibody complex.
Yokota
Akiko
A
Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 07, Aoba-ku, Sendai 980-8579, Japan.
Tsumoto
Kouhei
K
Shiroishi
Mitsunori
M
Kondo
Hidemasa
H
Kumagai
Izumi
I
D000818:Animals; D000936:Antigen-Antibody Complex / Q000737:chemistry*; D002645:Chickens; D006860:Hydrogen Bonding; D007128:Immunoglobulin Fragments / Q000737:chemistry* / Q000276:immunology; D009113:Muramidase / Q000737:chemistry* / Q000276:immunology; D014867:Water / Q000737:chemistry
D000936:Antigen-Antibody Complex; D007128:Immunoglobulin Fragments; D014867:Water; D009113:Muramidase