J. Biol. Chem., Vol. 265, Issue 1, 133-138, 01, 1990
Active site structure and antigen binding properties of idiotypically cross-reactive anti-fluorescein monoclonal antibodies
WD Bedzyk, JN Herron, AB Edmundson and EW Voss Jr
Department of Microbiology, University of Illinois, Urbana 61801.
This report includes complete VH and V kappa nucleotide and deduced amino
acid sequences of idiotypically cross-reactive monoclonal anti- fluorescein
antibodies that differed greater than 10(5)-fold in affinity. High affinity
monoclonal antibody 4-4-20 and intermediate affinity antibodies 10-25,
5-14, 9-40, 12-40, and 3-24 utilized greater than or equal to 90%
homologous VHIIIC germ-line genes. Extensive D segment length and sequence
variability were observed; however, compensatory germ-line JH4 (4-4-20 and
3-24) or JH3 (10-25, 5-14, 9-40, and 12-40) sequence lengths resulted in H
chain CDR3 + FR4 to be a constant 18 amino acids. In addition, each
antibody and low affinity 3- 13 rearranged greater than or equal to 96%
homologous V kappa II genes to J kappa 1, except for 10-25 (J kappa 5) and
3-13 (J kappa 4). Resolved crystal structure of complexed fluorescein and
4-4-20 Fab fragments revealed residues HisL27d, TyrL32, ArgL34, SerL91,
TrpL96, and TrpH33 acted as hapten contact residues. Antibodies 5-14, 9-40,
12- 40, and 3-24 primary structures possessed identical contact residues as
4-4-20 except for the substitution of HisL34 for ArgL34. Thus, ArgL34 was
implicated in the increased affinity of monoclonal antibody 4-4-20.
Finally, it was difficult to correlate extensive H chain CDR3 residue
heterogeneity directly with fluorescein binding and idiotypy.