The invariant tryptophan in an H chain V region is not essential to antibody binding.
The first amino acid residue of the second framework region in all antibody H and L chain V regions sequenced to date is invariably tryptophan. To test whether this invariance is essential to proper domain folding and generation of a functional antibody, the tryptophan residue in the heavy chain V region of a mouse anti-p-azophenylarsonate antibody was converted to an alanine residue by oligonucleotide-directed mutagenesis of the H chain gene. The mutant gene was transfected into mouse hybridoma cells that produce the homologous L chain, and the resulting mutant antibody was purified from the cell supernatant. It was shown to have essentially the same reactivity as wild type toward a series of anti-idiotypic antibodies and to bind Ag with a Ka similar to that of wild type.
D000595:Amino Acid Sequence; D000818:Animals; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D011994:Recombinant Proteins / Q000378:metabolism; D014364:Tryptophan
D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D011994:Recombinant Proteins; D014364:Tryptophan