Evidence of allosteric conformational changes in the antibody constant region upon antigen binding.
We have addressed the question of whether antigen binding induces a conformational change in the heavy chain constant (C(H)) domain of antibodies using staphylococcal protein A or streptococcal protein G as probes, since these proteins are known to bind to IgG domains such as C(H)1 and C(H)2-C(H)3 domains. Biosensor assays on interactions between these proteins and mouse IgG specific to (4-hydroxy-3-nitrophenyl)acetyl (NP) or their enzymatic fragments conducted in the presence or absence of the hapten, NP-epsilon-aminocaproic acid (NP-Cap), showed that the binding of IgG to these proteins was inhibited by the binding of NP-Cap. The results of isothermal titration calorimetry also revealed that the association constant for the interaction of protein A with IgG2b decreased by the addition of NP-Cap. These results suggested that antigen binding induced conformational changes in binding sites for protein G or protein A located at C(H)1 and C(H)2-C(H)3 domains, respectively.
Oda
Masayuki
M
Research Institute for Biological Sciences, Tokyo University of Science, 2669 Noda, Chiba 278-0022, Japan.
Kozono
Haruo
H
Morii
Hisayuki
H
Azuma
Takachika
T
D000494:Allosteric Regulation; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology / Q000378:metabolism*; D001666:Binding Sites, Antibody; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D011487:Protein Conformation
D000942:Antigens, Bacterial; D007074:Immunoglobulin G; C119204:streptococcal protective antigen