The antibody D2.3 catalyzes the hydrolysis of several p-nitrobenzyl and p-nitrophenyl esters with significant rate enhancement; product inhibition is observed with the former compounds but not with the latter. Whereas enzyme specificity has been extensively studied by X-ray crystallography, structural data on catalytic antibodies have thus far related only to one of the reactions they catalyze. To investigate the substrate specificity and the substrate relative to product selectivity of D2.3, we have determined the structures of its complexes with two p-nitrophenyl phosphonate transition state analogs (TSAs) and with the reaction product, p-nitrophenol. The complexes with these TSAs, determined at 1.9 A resolution, and that with p-nitrobenzyl phosphonate determined previously, differ mainly by the locations and conformations of the ligands. Taken together with kinetic data, the structures suggest that a hydrogen bond to an atom of the substrate distant by eight covalent bonds from the carbonyl group of the hydrolyzed ester bond contributes to catalytic efficiency and substrate specificity. The structure of Fab D2.3 complexed with p-nitrophenol was determined at 2.1 A resolution. Release of p-nitrophenol is facilitated due to the unfavourable interaction of the partial charge of the nitro group of p-nitrophenolate with the hydrophobic cavity where it is located, and to the absence of a direct hydrogen bond between the product and the Fab. Catalytic specificity and the manner of product release are both affected by interactions with substrate atoms remote from the reaction center that were not programmed in the design of the TSA used to elicit this antibody. Selection of a catalytic antibody that makes use of TSA unprogrammed features has been made practical because of the screening for catalytic efficiency incorporated in the procedure used to obtain it.
The line below this paragraph, {{ABSTRACT_PUBMED_9826512}}, adds the Publication Abstract to the page
(as it appears on PubMed at http://www.pubmed.gov), where 9826512 is the PubMed ID number.
-->
{{ABSTRACT_PUBMED_9826512}}
==About this Structure==
==About this Structure==
Line 24:
Line 28:
[[Category: Abzyme]]
[[Category: Abzyme]]
[[Category: Transition state analog]]
[[Category: Transition state analog]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 16:13:35 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 16:19:14 2008''
Revision as of 16:19, 28 July 2008
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
Full crystallographic information is available from OCA.
ReferenceReference
Crossreactivity, efficiency and catalytic specificity of an esterase-like antibody., Gigant B, Charbonnier JB, Eshhar Z, Green BS, Knossow M, J Mol Biol. 1998 Dec 4;284(3):741-50. PMID:9826512
