title: A mouse Ig kappa domain of very unusual framework structure loses function when converted to the consensus.
abstract: Antibody gene sequences, particularly those of kappa light chains, are very well conserved in the framework region, and the variability is concentrated in the complementarity-determining regions (CDR). We now found that the murine antibody 93-6 (Djavadi-Ohaniance, L., Friguet, B., and Goldberg, M. (1984) Biochemistry 23, 97-104) whose Fab fragment binds the beta-subunit of Escherichia coli tryptophan synthase with high affinity (Kd of 6.7.10(-9) M) has a highly unusual kappa light chain framework, which is crucial for the function of this antibody. It carries an insertion of 8 amino acids in a conserved framework loop that faces the antigen, and its framework region 2 (FR2) which precedes CDR2 is shortened by one amino acid, normally leucine and part of an absolutely conserved beta-bulge preceding CDR2. Removal of the insertion to restore the consensus sequence reduced the binding affinity of 93-6 by a factor 3, while insertion of the missing leucine into FR2 completely abolished binding.
authors.affiliation: Biochemisches Institut, Universität Zürich, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Ge
authors.forename: A
authors.initials: A
authors.lastname: Lupas
authors.forename: S
authors.initials: S
authors.lastname: Peraldi-Roux
authors.forename: S
authors.initials: S
authors.lastname: Spada
authors.forename: A
authors.initials: A
authors.lastname: Plückthun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000235:genetics*; D000937:Antigen-Antibody Reactions / Q000235:genetics*; D016384:Consensus Sequence; D017124:Conserved Sequence; D004926:Escherichia coli / Q000201:enzymology; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014367:Tryptophan Synthase / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D007145:Immunoglobulin kappa-Chains; D014367:Tryptophan Synthase