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2imd

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{{STRUCTURE_2imd| PDB=2imd | SCENE= }}
{{STRUCTURE_2imd| PDB=2imd | SCENE= }}
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'''Structure of SeMet 2-hydroxychromene-2-carboxylate isomerase (HCCA isomerase)'''
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===Structure of SeMet 2-hydroxychromene-2-carboxylate isomerase (HCCA isomerase)===
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==Overview==
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The enzyme 2-hydroxychromene-2-carboxylic acid (HCCA) isomerase catalyzes the glutathione (GSH)-dependent interconversion (Keq = 1.5) of HCCA and trans-o-hydroxybenzylidene pyruvic acid (tHBPA) in the naphthalene catabolic pathway of Pseudomonas putida. The dimeric protein binds one molecule of GSH very tightly (Kd approximately 5 nM) and a second molecule of GSH with much lower affinity (Kd approximately 2 to 11 microM). The enzyme is unstable in the absence of GSH. The turnover number in the forward direction (47 s(-1) at 25 degrees C) greatly exceeds off rates for GSH (koff approximately 10(-3) to 10(-2) s(-1) at 10 degrees C), suggesting that GSH acts as a tightly bound cofactor in the reaction. The crystal structure of the enzyme at 1.7 A resolution reveals that the isomerase is closely related to class kappa GSH transferases. Diffraction quality crystals could only be obtained in the presence of GSH and HCCA/tHBPA. Clear electron density is seen for GSH. Electron density for the organic substrates is located near the GSH and is best modeled to include both HCCA and tHBPA at occupancies of 0.5 for each. Although there is no electron density connecting the sulfur of GSH to the organic substrates, the sulfur is located very close (2.78 A) to C7 of HCCA. Taken together, the results suggest that the isomerization reaction involves a short-lived covalent adduct between the sulfur of GSH and C7 of the substrate.
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(as it appears on PubMed at http://www.pubmed.gov), where 17508726 is the PubMed ID number.
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{{ABSTRACT_PUBMED_17508726}}
==About this Structure==
==About this Structure==
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 07:39:09 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 02:54:03 2008''

Revision as of 23:54, 28 July 2008

Image:2imd.png

Template:STRUCTURE 2imd

Structure of SeMet 2-hydroxychromene-2-carboxylate isomerase (HCCA isomerase)

Template:ABSTRACT PUBMED 17508726

About this Structure

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

Reference

2-Hydroxychromene-2-carboxylic acid isomerase: a kappa class glutathione transferase from Pseudomonas putida., Thompson LC, Ladner JE, Codreanu SG, Harp J, Gilliland GL, Armstrong RN, Biochemistry. 2007 Jun 12;46(23):6710-22. Epub 2007 May 18. PMID:17508726

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