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2aaf

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{{STRUCTURE_2aaf| PDB=2aaf | SCENE= }}
{{STRUCTURE_2aaf| PDB=2aaf | SCENE= }}
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'''Structure of H278A arginine deiminase with L-arginine forming a S-alkylthiouronium reaction intermediate'''
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===Structure of H278A arginine deiminase with L-arginine forming a S-alkylthiouronium reaction intermediate===
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==Overview==
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L-arginine deiminase (ADI) catalyzes the irreversible hydrolysis of L-arginine to citrulline and ammonia. In a previous report of the structure of apoADI from Pseudomonas aeruginosa, the four residues that form the catalytic motif were identified as Cys406, His278, Asp280, and Asp166. The function of Cys406 in nucleophilic catalysis has been demonstrated by transient kinetic studies. In this study, the structure of the C406A mutant in complex with L-arginine is reported to provide a snapshot of the enzyme.substrate complex. Through the comparison of the structures of apoenzyme and substrate-bound enzyme, a substrate-induced conformational transition, which might play an important role in activity regulation, was discovered. Furthermore, the position of the guanidinium group of the bound substrate relative to the side chains of His278, Asp280, and Asp166 indicated that these residues mediate multiple proton transfers. His278 and Asp280, which are positioned to activate the water nucleophile in the hydrolysis of the S-alkylthiouronium intermediate, were replaced with alanine to stabilize the intermediate for structure determination. The structures determined for the H278A and D280A mutants co-crystallized with L-arginine provide a snapshot of the S-alkylthiouronium adduct formed by attack of Cys406 on the guanidinium carbon of L-arginine followed by the elimination of ammonia. Asp280 and Asp166 engage in ionic interactions with the guanidinium group in the C406A ADI. L-arginine structure and might orient the reaction center and participate in proton transfer. Structure determination of D166A revealed the apoD166A ADI. The collection of structures is interpreted in the context of recent biochemical data to propose a model for ADI substrate recognition and catalysis.
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{{ABSTRACT_PUBMED_16091358}}
==About this Structure==
==About this Structure==
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[[Category: L-arginine deiminase]]
[[Category: L-arginine deiminase]]
[[Category: X-ray structure]]
[[Category: X-ray structure]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 07:29:11 2008''

Revision as of 04:29, 28 July 2008

Image:2aaf.png

Template:STRUCTURE 2aaf

Structure of H278A arginine deiminase with L-arginine forming a S-alkylthiouronium reaction intermediate

Template:ABSTRACT PUBMED 16091358

About this Structure

2AAF is a Single protein structure of sequence from Pseudomonas aeruginosa. Full crystallographic information is available from OCA.

Reference

Crystal structures representing the Michaelis complex and the thiouronium reaction intermediate of Pseudomonas aeruginosa arginine deiminase., Galkin A, Lu X, Dunaway-Mariano D, Herzberg O, J Biol Chem. 2005 Oct 7;280(40):34080-7. Epub 2005 Aug 9. PMID:16091358

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