SNAPSHOTS ALONG THE REACTION COORDINATE OF AN S(N)AR REACTION CATALYZED BY GLUTATHIONE TRANSFERASE

The three-dimensional structures of a class mu glutathione transferase in complex with a transition-state analogue, 1-(S-glutathionyl)-2,4,6-trinitrocyclohexadienate, and a product, 1-(S-glutathionyl)-2,4-dinitrobenzene, of a nucleophilic aromatic substitution (S(N)Ar) reaction have been determined at 1.9- and 2.0-angstrom resolution, respectively. The two structures represent snapshots along the reaction coordinate for the enzyme-catalyzed reaction of glutathione with 1-chloro-2,4-dinitrobenzene and reveal specific interactions between the enzyme, intermediate, and product that are important in catalysis. The geometries of the intermediate and product are used to postulate reaction coordinate motion during catalysis.