1GAF: 48G7 HYBRIDOMA LINE FAB COMPLEXED WITH HAPTEN 5-(PARA-NITROPHENYL PHOSPHONATE)-PENTANOIC ACID

Citation:
Abstract
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.
PDB ID: 1GAFDownload
MMDB ID: 49220
PDB Deposition Date: 1996/2/6
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.95  Å
Source Organism:
Similar Structures:
Biological Unit for 1GAF: dimeric; determined by author and by software (PISA)
Molecular Components in 1GAF
Label Count Molecule
Proteins (2 molecules)
1
Chimeric 48g7 FAB(Gene symbol: IGKC)
Molecule annotation
1
Chimeric 48g7 FAB(Gene symbol: IGHG1)
Molecule annotation
Chemical (1 molecule)
1
1
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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