Quantitative account of the enhanced affinity of two linked scFvs specific for different epitopes on the same antigen.
Protein and other antigens typically have a number of different epitopes. This presents an opportunity for designing high-affinity antibodies by connecting via a flexible peptide linker two antibody fragments recognizing non-overlapping epitopes on the same antigen. The same strategy was employed in natural and designed DNA-binding proteins. According to a previous theory, the linking enhances the antigen-binding affinity over those of the individual antibody fragments (with association constants K(A) and K(B)) by p(d(0))K(B) or p(d(0))K(A), where p(d(0))=(3/4pil(p)bL)(3/2)exp(-3d(0)(2)/4l(p)bL)(1-5l(p)/4bL+ cdots, three dots, centered ) is the probability density for the end-to-end vector of the flexible linker with L residues to have a distance d(0). The predicted affinity enhancement is found to be actually approached by a bi-specific antibody against hen egg lysozyme consisting of scFv fragments of D1.3 and HyHEL-10. The wide applicability of the theory is demonstrated by diverse examples of protein-protein interactions constrained by flexible linkers.
Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA. hxzhou@csit.fsu.edu
Huan-Xiang
HX
Zhou
D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology*; D000915:Antibody Affinity / Q000276:immunology*; D000918:Antibody Specificity; D001665:Binding Sites; D001666:Binding Sites, Antibody; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000276:immunology*; D008956:Models, Chemical; D009113:Muramidase / Q000276:immunology*; D011487:Protein Conformation; D015202:Protein Engineering; D017510:Protein Folding; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism
D018033:Antibodies, Bispecific; D004268:DNA-Binding Proteins; D000939:Epitopes; D007135:Immunoglobulin Variable Region; D014157:Transcription Factors; C421864:hen egg lysozyme; D009113:Muramidase