1t9c

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spinqualitylabelsall models 1t9c, resolution 2.34Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure Of Yeast Acetohydroxyacid Synthase In Complex With A Sulfonylurea Herbicide, Sulfometuron methyl

Overview

Acetohydroxyacid synthase (AHAS, EC 2.2.1.6) is the target for the, sulfonylurea herbicides, which act as potent inhibitors of the enzyme., Chlorsulfuron (marketed as Glean) and sulfometuron methyl (marketed as, Oust) are two commercially important members of this family of herbicides., Here we report crystal structures of yeast AHAS in complex with, chlorsulfuron (at a resolution of 2.19 A), sulfometuron methyl (2.34 A), and two other sulfonylureas, metsulfuron methyl (2.29 A) and tribenuron, methyl (2.58 A). The structures observed suggest why these inhibitors have, different potencies and provide clues about the differential effects of, mutations in the active site tunnel on various inhibitors. In all of the, structures, the thiamin diphosphate cofactor is fragmented, possibly as, the result of inhibitor binding. In addition to thiamin diphosphate, AHAS, requires FAD for activity. Recently, it has been reported that reduction, of FAD can occur as a minor side reaction due to reaction with the, carbanion/enamine of the hydroxyethyl-ThDP intermediate that is formed, midway through the catalytic cycle. Here we report that the isoalloxazine, ring has a bent conformation that would account for its ability to accept, electrons from the hydroxyethyl intermediate. Most sequence and mutation, data suggest that yeast AHAS is a high-quality model for the plant enzyme.

About this Structure

1T9C is a Single protein structure of sequence from Saccharomyces cerevisiae with K, MG, 1SM, P23, FAD and P22 as ligands. Active as Acetolactate synthase, with EC number 2.2.1.6 Full crystallographic information is available from OCA.

Reference

Elucidating the specificity of binding of sulfonylurea herbicides to acetohydroxyacid synthase., McCourt JA, Pang SS, Guddat LW, Duggleby RG, Biochemistry. 2005 Feb 22;44(7):2330-8. PMID:15709745

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