The difference of binding epitopes on human CD16 (FcgammaRIII) interacted with hIgG1 and monoclonal antibody B88-9.
The 3-D complex structures of extracellular domain of human CD16 (FcgammaRIII) and hIgG1 or B88-9 were obtained by means of computer-guided molecular modeling, respectively. The binding epitopes were predicted and binding energy was calculated theoretically. The epitopes of human CD16 interacted with hIgG1 and B88-9 were different and the binding energy of B88-9 was stronger than hIgG1. The computer competing simulation results showed that B88-9 could bind to CD16 when CD16 was also bound by hIgG1, while IgG1 could not bind to CD16 after CD16 was bound by B88-9. By flow cytometry analysis, the competitive binding activity of B88-9 to CD16 with hIgG1 was evaluated. With the increasing concentrations of hIgG1, the binding activity of B88-9 was not interfered markedly. It suggested that hIgG1 could not inhibit the interaction of CD16 and B88-9 and the binding domain of hIgG1 and B88-9 on CD16 was different.
Feng
Jiannan
J
Beijing Institute of Basic Medical Sciences, PO Box 130 (3), Beijing 100850, PR China. fengjn@nic.bmi.ac.cn
Xie
Zhigang
Z
Yu
Ming
M
Guo
Ning
N
Shen
Beifen
B
D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology; D001665:Binding Sites; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D000939:Epitopes / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry / Q000378:metabolism; D007074:Immunoglobulin G / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D017452:Receptors, IgG / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000939:Epitopes; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D017452:Receptors, IgG