title: The mitochondrial F1FO-ATPase desensitization to oligomycin by tributyltin is due to thiol oxidation.
abstract: The antibiotic oligomycin is known to inhibit mitochondrial F-type ATP synthases. The antibiotic inhibits both ATP synthesis and hydrolysis by blocking the H(+) translocation through FO which is coupled to the catalytic activity of F1. The amphiphilic organotin tri-n-butyltin (TBT), a known mitochondrial poison, can penetrate into biological membranes and covalently bind to electron-donor atoms of biomolecules such as sulfur. This study aims at exploring the mechanism(s) involved in the enzyme desensitization to oligomycin which occurs at concentrations >1 μM TBT. This poorly known effect of TBT, which only appeared at temperatures above the break in the Arrhenius plot of the enzyme activity, was found to be accompanied by the oxidation of isolated thiol groups of the mitochondrial complex. The oligomycin sensitivity was restored by the reducing agents glutathione and dithioerythritol and not influenced by antioxidants. The whole of data is consistent with the hypothesis that thiol oxidation is caused by TBT covalent binding to cysteine residues in a low-affinity site on FO and not by other possible oxidative events. According to this putative model, the onset of tin-sulfur bonds would trigger conformational changes and weaken the oligomycin interaction with FO.
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Nesci
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Ventrella
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Trombetti
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pirini
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy. Electronic address: alessandra.pagliarani@unibo.it.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pagliarani
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004226:Dithioerythritol / Q000494:pharmacology; D004336:Drug Antagonism; D005978:Glutathione / Q000494:pharmacology; D007700:Kinetics; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000201:enzymology; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011794:Quercetin / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013552:Swine; D013816:Thermodynamics; D014220:Trialkyltin Compounds / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D024101:Mitochondrial Proteins; D009840:Oligomycins; D013438:Sulfhydryl Compounds; D014220:Trialkyltin Compounds; C011559:tributyltin; D004226:Dithioerythritol; D011794:Quercetin; D017301:Ca(2+) Mg(2+)-ATPase; D006180:Proton-Translocating ATPases; D005978:Glutathione
keywords: 1,4-dithioerythritol; 5,5′-dithiobis(2-nitrobenzoic acid); ARS; ASC; BSA; DTE; DTNB; F(1)F(O)-ATPase; N-ethylmaleimide; NEM; OI Mg-ATPase; OS Mg-ATPase; Oligomycin; TBT; TOC; Thiol oxidation; Tm; Tri-n-butyltin; bovine serum albumin; l-ascorbate; melting temperature; oligomycin-insensitive Mg-ATPase; oligomycin-sensitive Mg-ATPase; sodium (meta) arsenite; tri-n-butyltin; α-tocopherol