5fwg

From Proteopedia

Revision as of 18:36, 18 December 2007

TETRA-(5-FLUOROTRYPTOPHANYL)-GLUTATHIONE TRANSFERASE

Overview

The three-dimensional structures of isoenzyme 3-3 of glutathione (GSH), transferase complexed with (9R,10R)- and, (9S,10S)-9-(S-glutathionyl)-10-hydroxy-9,10-dihydrophenanthrene, [(9R,10R)-2 and (9S,10S)-2], which are the products of the addition of GSH, to phenanthrene 9,10-oxide, have been determined at resolutions of 1.9 and, 1.8 A, respectively. The structures indicate that the xenobiotic substrate, binding site is a hydrophobic cavity defined by the side chains of Y6, W7, V9, and L12 from domain I (the GSH binding domain) and I111, Y115, F208, and S209 in domain II of the protein. All of these residues are located in, variable-sequence regions of the primary structure of class mu isoenzymes., Three of the eight residues (V9, I111, and S209) of isoenzyme 3-3 that are, in direct van der Waals contact with the dihydrophenanthrenyl portion of, the products are mutated (V9I, I111A, and S209A) in the related isoenzyme, 4-4. These three residues are implicated in control of the, stereoselectivity of the class mu isoenzymes. The hydroxyl group of Y115, is found to be hydrogen-bonded to the 10-hydroxyl group of (9S,10S)-2, a, fact suggesting that this residue could act as an electrophile to, stabilize the transition state for the addition of GSH to epoxides. The, Y115F mutant isoenzyme 3-3 is about 100-fold less efficient than the, native enzyme in catalyzing the addition of GSH to phenanthrene 9,10-oxide, and about 50-fold less efficient in the Michael addition of GSH to, 4-phenyl-3-buten-2-one. The side chain of Y115 is positioned so as to act, as a general-acid catalytic group for two types of reactions that would, benefit from electrophilic assistance. The results are consistent with the, notion that domain II, which harbors most of the variability in primary, structure, plays a crucial role in defining the substrate specificity of, class mu isoenzymes.

About this Structure

5FWG is a Single protein structure of sequence from Rattus norvegicus with GPR as ligand. Active as Glutathione transferase, with EC number 2.5.1.18 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Structure and function of the xenobiotic substrate binding site of a glutathione S-transferase as revealed by X-ray crystallographic analysis of product complexes with the diastereomers of 9-(S-glutathionyl)-10-hydroxy-9,10-dihydrophenanthrene., Ji X, Johnson WW, Sesay MA, Dickert L, Prasad SM, Ammon HL, Armstrong RN, Gilliland GL, Biochemistry. 1994 Feb 8;33(5):1043-52. PMID:8110735

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