Differences in heavy chain amino acid sequences affecting the specificity of antibodies for variants of cytochrome c.
In a previous study [Goshorn et al. (1991) J. biol. Chem. 266, 2134-2142], several mAb specific for the same region on different cytochromes c were shown to have similar H or L chains. To determine the effect of differences in individual chains on antigenic variant specificity in the present study, chimeric mAb were prepared by recombining the H and L chains of mAb having the same or a different cytochrome c specificity. The H and L chains of two mAb to the region around residue 60 on horse cytochrome c (1F5.D1 and 2E5.G10) were functionally interchangeable even though the H chain differed by 11 amino acid residues in the complementarity-determining regions (CDR) and 15 amino acids overall in the variable regions. The L chains only differed by four amino acid residues in the CDR (five residues overall). Neither the H nor L chain of a mAb binding the same region of rat cytochrome c (6H2.B4) was functionally interchangeable with the chains of the two horse cytochrome c-specific mAb. The L chain of this mAb is very different from the other L chains which were derived from a different V kappa family, but the H chain is nearly as similar to the horse cytochrome c-specific H chains as they are to each other. Most of the differences occur in CDR3 and result from the use of a distinct DH segment. The results indicate that, in some cases, the specificity of a mAb for a particular variant of a protein Ag, at least in regard to the H chain, is determined by only a few amino acid differences. The differences in the sequences of the H chains of the three mAb in this study and in the structures of their specific Ag provide insight into a possible molecular basis for the specificity of these mAb.
Jemmerson
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R
Department of Microbiology, University of Minnesota Medical School, Minneapolis 55455.
Mueller
C
C
Flaa
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D
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D001483:Base Sequence; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000276:immunology*; D006736:Horses; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D011993:Recombinant Fusion Proteins
D000911:Antibodies, Monoclonal; D003574:Cytochrome c Group; D007143:Immunoglobulin Heavy Chains; D011993:Recombinant Fusion Proteins