Arsenate reduction: thiol cascade chemistry with convergent evolution.

TitleArsenate reduction: thiol cascade chemistry with convergent evolution.
Publication TypeJournal Article
Year of Publication2006
AuthorsMessens, J., and S. Silver
JournalJ Mol Biol
Volume362
Issue1
Pagination1-17
Date Published2006 Sep 8
Type of Articleredox
ISSN0022-2836
KeywordsAnimals, Arsenates, Arsenic, Bacterial Proteins, Evolution, Molecular, Fungal Proteins, Glutaredoxins, Models, Molecular, Oxidation-Reduction, Oxidoreductases, Protein Conformation, Sulfhydryl Compounds
Abstract

The frequent abundance of arsenic in the environment has guided the evolution of enzymes for the reduction of arsenate. The arsenate reductases (ArsC) from different sources have unrelated sequences and structural folds, and can be divided into different classes on the basis of their structures, reduction mechanisms and the locations of catalytic cysteine residues. The thioredoxin-coupled arsenate reductase class is represented by Staphylococcus aureus pI258 ArsC and Bacillus subtilis ArsC. The ArsC from Escherichia coli plasmid R773 and the eukaryotic ACR2p reductase from Saccharomyces cerevisiae represent two distinct glutaredoxin-linked ArsC classes. All are small cytoplasmic redox enzymes that reduce arsenate to arsenite by the sequential involvement of three different thiolate nucleophiles that function as a redox cascade. In contrast, the ArrAB complex is a bacterial heterodimeric periplasmic or a surface-anchored arsenate reductase that functions as a terminal electron acceptor and transfers electrons from the membrane respiratory chain to arsenate. Finally, the less well documented arsenate reductase activity of the monomeric arsenic(III) methylase, which is an S-adenosylmethionine (AdoMet)-dependent methyltransferase. After each oxidative methylation cycle and before the next methylation step, As(V) is reduced to As(III). Methylation by this enzyme is also considered an arsenic-resistance mechanism for bacteria, fungi and mammals.

DOI10.1016/j.jmb.2006.07.002
Alternate JournalJ. Mol. Biol.
PubMed ID16905151
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