Publication Date:
1994-08-19
Description:
The three-dimensional structure of an unusually active hydrolytic antibody with a phosphonate transition state analog (hapten) bound to the active site has been solved to 2.5 A resolution. The antibody (17E8) catalyzes the hydrolysis of norleucine and methionine phenyl esters and is selective for amino acid esters that have the natural alpha-carbon L configuration. A plot of the pH-dependence of the antibody-catalyzed reaction is bell-shaped with an activity maximum at pH 9.5; experiments on mechanism lend support to the formation of a covalent acyl-antibody intermediate. The structural and kinetic data are complementary and support a hydrolytic mechanism for the antibody that is remarkably similar to that of the serine proteases. The antibody active site contains a Ser-His dyad structure proximal to the phosphorous atom of the bound hapten that resembles two of the three components of the Ser-His-Asp catalytic triad of serine proteases. The antibody active site also contains a Lys residue to stabilize oxyanion formation, and a hydrophobic binding pocket for specific substrate recognition of norleucine and methionine side chains. The structure identifies active site residues that mediate catalysis and suggests specific mutations that may improve the catalytic efficiency of the antibody. This high resolution structure of a catalytic antibody-hapten complex shows that antibodies can converge on active site structures that have arisen through natural enzyme evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhou, G W -- Guo, J -- Huang, W -- Fletterick, R J -- Scanlan, T S -- DK39304/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1994 Aug 19;265(5175):1059-64.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8066444" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Sequence
;
Antibodies, Catalytic/*chemistry/immunology/metabolism
;
Binding Sites
;
Computer Graphics
;
Crystallization
;
Crystallography, X-Ray
;
Haptens/metabolism
;
Hydrogen Bonding
;
Hydrogen-Ion Concentration
;
Hydrolysis
;
Models, Molecular
;
Molecular Sequence Data
;
Protein Conformation
;
Serine Endopeptidases/*chemistry/metabolism
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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