Publication Date:
1996-02-23
Description:
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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Patten, P A -- Gray, N S -- Yang, P L -- Marks, C B -- Wedemayer, G J -- Boniface, J J -- Stevens, R C -- Schultz, P G -- R01 AL24695/PHS HHS/ -- New York, N.Y. -- Science. 1996 Feb 23;271(5252):1086-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, CA 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8599084" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Sequence
;
Animals
;
Antibodies, Catalytic/chemistry/genetics/*immunology/metabolism
;
Antibody Affinity
;
Antigen-Antibody Complex
;
Antigen-Antibody Reactions
;
Base Sequence
;
Binding Sites
;
Catalysis
;
Cloning, Molecular
;
Crystallization
;
Crystallography, X-Ray
;
*Evolution, Molecular
;
Genes, Immunoglobulin
;
Haptens/immunology
;
Immunoglobulin Fab Fragments/genetics/immunology
;
Immunoglobulin Heavy Chains/genetics/immunology
;
Immunoglobulin Light Chains/genetics/immunology
;
Mice
;
Molecular Sequence Data
;
Mutation
;
Protein Conformation
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
Permalink
