title: Tellurite-mediated disabling of [4Fe-4S] clusters of Escherichia coli dehydratases.
abstract: The tellurium oxyanion tellurite is toxic for most organisms and it seems to alter a number of intracellular targets. In this work the toxic effects of tellurite upon Escherichia coli [4Fe-4S] cluster-containing dehydratases was studied. Reactive oxygen species (ROS)-sensitive fumarase A (FumA) and aconitase B (AcnB) as well as ROS-resistant fumarase C (FumC) and aconitase A (AcnA) were assayed in cell-free extracts from tellurite-exposed cells in both the presence and absence of oxygen. While over 90 % of FumA and AcnB activities were lost in the presence of oxygen, no enzyme inactivation was observed in anaerobiosis. This result was not dependent upon protein biosynthesis, as determined using translation-arrested cells. Enzyme activity of purified FumA and AcnB was inhibited when exposed to an in vitro superoxide-generating, tellurite-reducing system (ITRS). No inhibitory effect was observed when tellurite was omitted from the ITRS. In vivo and in vitro reconstitution experiments with tellurite-damaged FumA and AcnB suggested that tellurite effects involve [Fe-S] cluster disabling. In fact, after exposing FumA to ITRS, released ferrous ion from the enzyme was demonstrated by spectroscopic analysis using the specific Fe(2+) chelator 2,2'-bipyridyl. Subsequent spectroscopic paramagnetic resonance analysis of FumA exposed to ITRS showed the characteristic signal of an oxidatively inactivated [3Fe-4S](+) cluster. These results suggest that tellurite inactivates enzymes of this kind via a superoxide-dependent disabling of their [4Fe-4S] catalytic clusters.
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Iván L
authors.initials: IL
authors.lastname: Calderón
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Alex O
authors.initials: AO
authors.lastname: Elías
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Eugenia L
authors.initials: EL
authors.lastname: Fuentes
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Gonzalo A
authors.initials: GA
authors.lastname: Pradenas
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Miguel E
authors.initials: ME
authors.lastname: Castro
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Felipe A
authors.initials: FA
authors.lastname: Arenas
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: José M
authors.initials: JM
authors.lastname: Pérez
authors.affiliation: Laboratorio de Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Claudio C
authors.initials: CC
authors.lastname: Vásquez
mesh_terms: D000154:Aconitate Hydratase / Q000037:antagonists & inhibitors; D000332:Aerobiosis; D000693:Anaerobiosis; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry / Q000378:metabolism; D005649:Fumarate Hydratase / Q000037:antagonists & inhibitors; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D019746:Intramolecular Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D013057:Spectrum Analysis; D013481:Superoxides / Q000378:metabolism; D013691:Tellurium / Q000009:adverse effects*
chemical_list: D005296:Ferrous Compounds; D007506:Iron-Sulfur Proteins; D013481:Superoxides; D006836:Hydro-Lyases; C095842:fumarase C; D005649:Fumarate Hydratase; D000154:Aconitate Hydratase; D019746:Intramolecular Oxidoreductases; C048474:oxaloacetate tautomerase; C026660:tellurous acid; D013691:Tellurium