Tellurite-mediated disabling of [4Fe-4S] clusters of Escherichia coli dehydratases

Iván L. Calderón, Alex O. Elías, Eugenia L. Fuentes, Gonzalo A. Pradenas, Miguel E. Castro, Felipe A. Arenas, José M. Pérez, Claudio C. Vásquez

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


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, telluriter-educing 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 Fe2+ 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.

Original languageEnglish (US)
Pages (from-to)1840-1846
Number of pages7
Issue number6
StatePublished - 2009
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology


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