2IMD

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

Summary for 2IMD

• Entry DOI: 10.2210/pdb2imd/pdb
• Related: 1R4W 2IME 2IMF
• Descriptor: 2-hydroxychromene-2-carboxylate isomerase, PHOSPHATE ION, GLUTATHIONE, ... (7 entities in total)
• Functional Keywords: isomerase, glutathione, kgst, kappa gst, transferase
• Biological source: Pseudomonas putida
• Total number of polymer chains: 1
• Total formula weight: 24467.46

Authors

Thompson, L.C.,Ladner, J.E.,Codreanu, S.G.,Harp, J.,Gilliland, G.L.,Armstrong, R.N. (deposition date: 2006-10-04, release date: 2007-06-12, Last modification date: 2017-10-11)

Primary citation

Thompson, L.C.,Ladner, J.E.,Codreanu, S.G.,Harp, J.,Gilliland, G.L.,Armstrong, R.N.
2-Hydroxychromene-2-carboxylic Acid Isomerase: A Kappa Class Glutathione Transferase from Pseudomonas putida
Biochemistry, 46:6710-6722, 2007

PubMed Abstract: 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.

PubMed: 17508726
DOI: 10.1021/bi700356u

Experimental method

X-RAY DIFFRACTION (1.6 Å)