1GAF image
Deposition Date 1996-02-06
Release Date 1996-07-11
Last Version Date 2024-11-20
Entry Detail
PDB ID:
1GAF
Title:
48G7 HYBRIDOMA LINE FAB COMPLEXED WITH HAPTEN 5-(PARA-NITROPHENYL PHOSPHONATE)-PENTANOIC ACID
Biological Source:
Source Organism:
Homo sapiens (Taxon ID: 9606)
Host Organism:
Method Details:
Experimental Method:
Resolution:
1.95 Å
R-Value Free:
0.30
R-Value Work:
0.24
R-Value Observed:
0.24
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:CHIMERIC 48G7 FAB
Gene (Uniprot):IGHG1
Chain IDs:B (auth: H)
Chain Length:217
Number of Molecules:1
Biological Source:Homo sapiens
Polymer Type:polypeptide(L)
Molecule:CHIMERIC 48G7 FAB
Chain IDs:A (auth: L)
Chain Length:214
Number of Molecules:1
Biological Source:Homo sapiens
Ligand Molecules
Primary Citation
The immunological evolution of catalysis.
Science 271 1086 1091 (1996)
PMID: 8599084

Abstact

The germline genes used by the mouse to generate the esterolytic antibody 48G7 were cloned and expressed in an effort to increase our understanding of the detailed molecular mechanisms by which the immune system evolves catalytic function. The nine replacement mutations that were fixed during affinity maturation increased affinity for the transition state analogue by a factor of 10(4), primarily the result of a decrease in the dissociation rate of the hapten-antibody complex. There was a corresponding increase in the rate of reaction of antibody with substrate, k(cat)/k(m), from 1.7 x 10(2)M(-1) min(-1) to 1.4 x 10(4)M(-1) min(-1). The three-dimensional crystal structure of the 48G7-transition state analogue complex at 2.0 angstroms resolution indicates that one of the nine residues in which somatic mutations have been fixed directly contact the hapten. Thus, in the case of 48G7, affinity maturation appears to play a conformational role, either in reorganizing the active site geometry of limiting side-chain and backbone flexibility of the germline antibody. The crystal structure and analysis of somatic and directed active site mutants underscore the role of transition state stabilization in the evolution of this catalytic antibody.

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Primary Citation of related structures