dimethyl(2-hydroxy-5-nitrobenzyl)sulfonium and 1-anilino-8-naphthalenesulfonate

2-Hydroxy-5-nitrobenzyl alcohol (HNB) was prepared from dimethyl(2-hydroxyl-5-nitrobenzyl)sulfonium bromide (HNBB). HNB binds to glutathione S-transferases (GSTs) 1-2 and 2-2 with moderate affinity at a site separate from 1-anilino-8-naphthalenesulfonate (ANS). Intrinsic fluorescence due to Trp-21 is strongly quenched by HNB binding but there is no effect on catalytic activity. There appear to be two HNB binding sites per dimer in each GST isoenzyme. We suggest that HNB binds directly at Trp-21 of each subunit and that previously reported quenching of intrinsic fluorescence in these proteins upon ligand binding may be due to indirect structural effects rather than direct binding at this residue.

Topics: Anilino Naphthalenesulfonates; Animals; Benzyl Alcohols; Binding Sites; Fluorescent Dyes; Glutathione Transferase; Indicators and Reagents; Isoenzymes; Ligands; Molecular Structure; Nitrobenzenes; Protein Binding; Rats; Spectrometry, Fluorescence; Sulfonium Compounds; Tryptophan