Arsenate reduction mediated by the plasmid‐encoded ArsC protein is coupled to glutathione

Abstract

Resistance to arsenate conferred on Escherichia coii by the are operon of piasmid R773 requires both the product of the arsC gene and reduction of arsenate to arsenite. A genetic anaiysis was performed to identify the source of reducing potentiai in vivo, in addition to the ars genes, arsenate resistance required the products of the gor gene for glutathione reductase and the gshA and gshB genes for glutathione synthesis. Mutations in the trx and grx genes for thioredoxin and giutaredoxin, respectiveiy, had no effect on arsenate resistance. Aithough resistance required the arsC gene, the rate of reduction of arsenate to arsenite was nearly the same in ceiis iacking the ars operon. in strains deficient in giutathione biosynthesis this endogenous reduction was greatly diminished, and cells exhibited increased sensitivity to arsenate. When giutathione was supplied exogenously to such mutants, resistance was restored only to ceiis expressing the ars operon, and oniy such ceiis had detectable arsenate reduction after addition of glutathione. Since ArsC-catalysed reduction of arsenate provides high ievei resistance, physicai coupiing of the ArsC reaction to efflux of the resuiting arsenite is hypothesised.

Virulence and arsenic resistance in Yersiniae

“…The arsR, -B, and -C gene products resemble those encoded by the E. coli chromosome (52). ArsR is an arseniteinducible transcriptional repressor (67,68), ArsB forms a transmembrane channel (19,47,59), and ArsC catalyzes the reduction of arsenate to arsenite, which is in turn extruded by the transport system (23,26,27,39). Although arsH has no counterpart in other ars operons, it is nevertheless required for As resistance.…”

Natural variation in arsenate tolerance identifies an arsenate reductase in Arabidopsis thaliana

“…OD 600 nm was measured, all cultures were diluted with low Pi medium 43 to OD 600 nm ¼ 0.2 and allowed to grow, alone or with 1 mM As(V) (30°C, 24 h). Since most As(III) is extruded in bacteria, cultures were centrifuged and 1 ml of supernatant was collected.…”

The Shoot-Specific Expression of γ-Glutamylcysteine Synthetase Directs the Long-Distance Transport of Thiol-Peptides to Roots Conferring Tolerance to Mercury and Arsenic

“…Arabidopsis plants deficient in root phosphate transporters are moderately resistant to arsenate (Shin et al, 2004). Arsenate is efficiently reduced into arsenite (AsO 3 23 ) by GSH-dependent arsenate reductase activities in bacteria, fungi, plants, and animals (Oden et al, 1994;Mukhopadhyay et al, 1998;Dhankher et al, 2002Dhankher et al, , 2006Dong et al, 2005). Arsenite is highly thiolreactive and may be chelated and sequestrated as As(S-R) 3 thiol-peptide complexes during its detoxification (Dey et al, 1994;Rosen, 1999;Sharples et al, 2000).…”