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.
Highlights
From the IlBiochemisches Institut, Unioersitiit Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland and the t-Protein Engineering Group, Max-Planck-Institut fur Biochemie, Am Klopferspitz, D-82152 Martinsried, Federal Republic of Germany
We 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 fJ-subunit ofEscherichia coli tryptophan synthase with high affinity (Kd of 6.7.10-9 M) has a highly unusual K 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 fJ-bulge preceding CDR2
Summary
Vol 270, No 21, 1ssue of May 26, pp. 12446-12451, 1995 Printed in U.S.A. A Mouse Ig tc Domain of Very Unusual Framework Structure Loses Function when Converted to the Consensus*. Those of K light chains, are very well conserved in the framework region, and the variability is concentrated in the complementarity-determining regions (CDR). (1984) Biochemistry 23, 97-104) whose Fab fragment binds the fJ-subunit ofEscherichia coli tryptophan synthase with high affinity (Kd of 6.7.10-9 M) has a highly unusual K light chain framework, which is crucial for the function of this antibody. This knowledge is based on about 30 crystal structures of antibody variable domains and about 103 sequences, mostly of human and murine origin (Kabat et al, 1991; Rees et al, 1994). We show that it loses function when converted back to the consensus
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