title: Binding of 2-hydroxy-5-nitrobenzyl alcohol to rat alpha class glutathione S-transferases; evidence for binding at tryptophan 21.
abstract: 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.
authors.affiliation: Department of Biochemistry, University College Cork, Ireland.
authors.forename: R M
authors.initials: RM
authors.lastname: McCarthy
authors.forename: P
authors.initials: P
authors.lastname: Farmer
authors.forename: D
authors.initials: D
authors.lastname: Sheehan
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D000818:Animals; D001592:Benzyl Alcohols / Q000138:chemical synthesis / Q000378:metabolism*; D001665:Binding Sites; D005456:Fluorescent Dyes / Q000378:metabolism; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism*; D007202:Indicators and Reagents / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D015394:Molecular Structure; D009578:Nitrobenzenes / Q000138:chemical synthesis / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D013050:Spectrometry, Fluorescence; D013452:Sulfonium Compounds / Q000378:metabolism / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D000817:Anilino Naphthalenesulfonates; D001592:Benzyl Alcohols; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D007527:Isoenzymes; D008024:Ligands; D009578:Nitrobenzenes; D013452:Sulfonium Compounds; C024586:dimethyl(2-hydroxy-5-nitrobenzyl)sulfonium; C099263:2-hydroxy-5-nitrobenzyl alcohol; C027132:1-anilino-8-naphthalenesulfonate; D014364:Tryptophan; D005982:Glutathione Transferase