title: Microbial arsenic: from geocycles to genes and enzymes.
abstract: Arsenic compounds have been abundant at near toxic levels in the environment since the origin of life. In response, microbes have evolved mechanisms for arsenic resistance and enzymes that oxidize As(III) to As(V) or reduce As(V) to As(III). Formation and degradation of organoarsenicals, for example methylarsenic compounds, occur. There is a global arsenic geocycle, where microbial metabolism and mobilization (or immobilization) are important processes. Recent progress in studies of the ars operon (conferring resistance to As(III) and As(V)) in many bacterial types (and related systems in Archaea and yeast) and new understanding of arsenite oxidation and arsenate reduction by respiratory-chain-linked enzyme complexes has been substantial. The DNA sequencing and protein crystal structures have established the convergent evolution of three classes of arsenate reductases (that is classes of arsenate reductases are not of common evolutionary origin). Proposed reaction mechanisms in each case involve three cysteine thiols and S-As bond intermediates, so convergent evolution to similar mechanisms has taken place.
authors.affiliation: Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors.forename: Rita
authors.initials: R
authors.lastname: Mukhopadhyay
authors.forename: Barry P
authors.initials: BP
authors.lastname: Rosen
authors.forename: L T
authors.initials: LT
authors.lastname: Phung
authors.forename: Simon
authors.initials: S
authors.lastname: Silver
mesh_terms: D053502:Arsenate Reductases; D001152:Arsenicals / Q000378:metabolism / Q000494:pharmacology; D053501:Arsenite Transporting ATPases; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016623:Ion Pumps / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D009876:Operon; D012440:Saccharomyces / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013210:Staphylococcus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D001152:Arsenicals; D016623:Ion Pumps; D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; C506971:ARR2 protein, S cerevisiae; D053502:Arsenate Reductases; D053501:Arsenite Transporting ATPases