Circular dichroism of hapten--antibody complexes: characterization of the combining sites of native and reformed MOPC-315 protein, its isolated subunits, and its Fv fragment.
Extrinsic Cotton effects generated by binding haptens to native and reformed MOPC-315 protein, its subunits, and its Fv fragment have been examined. The identity of the combining sites of native and reassociated proteins and Fv-315 was demonstrated by the identity of their circular dichroism (CD) difference spectra. The spectrum of TNP-aminocaproate complexed with L chains differed in maxima and minima and cross-over points and lacked the 495-nm CD peak of TNP-aminocaproate-MOPC-315 protein and Nalpha-TNP-tryptophan spectra. A negative 293-nm tryptophanyl CD band, present in spectra of MOPC-315 protins and Fv-315 but absent from spectra of L and H chains, was blue-shifted by haptens and may represent electronic interactions occurring within the MOPC-315 combining site between tryptophanyl and chromophoric residues of different subunits. This conclusion is supported by molecular models of the MOPC-315 combining site.
D000818:Animals; D001666:Binding Sites, Antibody; D002942:Circular Dichroism; D006241:Haptens; D007128:Immunoglobulin Fragments / Q000032:analysis; D007143:Immunoglobulin Heavy Chains / Q000032:analysis; D007147:Immunoglobulin Light Chains / Q000032:analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008961:Models, Structural; D009194:Myeloma Proteins / Q000032:analysis / Q000276:immunology*; D009374:Neoplasms, Experimental / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000032:analysis
D006241:Haptens; D007128:Immunoglobulin Fragments; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D009194:Myeloma Proteins; D011947:Receptors, Antigen, B-Cell