Plasmid-encoded resistance to arsenic and antimony

Kaur, Parjit; Rosen, Barry P.

doi:10.1016/0147-619x(92)90004-t

Cited by 106 publications

(60 citation statements)

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“…Bacterial resistance to arsenical and antimonial compounds results from active extrusion of the toxic oxyanions from the resistant cells (15). Efflux of arsenite from oxyanion resistant Escherichia coli cells is catalyzed by a pump whose genes are encoded on the conjugative R factor R773 (5,10).…”

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confidence: 99%

Dual mode of energy coupling by the oxyanion-translocating ArsB protein

1995

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The arsA and arsB genes of the ars operon of R-factor R773 confer arsenite resistance in Escherichia coli by coding for an anion-translocating ATPase. Arsenite resistance and the in vivo energetics of arsenite transport were compared in cells expressing the arsA and arsB genes and those expressing just the arsB gene. Cells expressing the arsB gene exhibited intermediate arsenite resistance compared with cells expressing both the arsA and arsB genes. Both types of cells exhibited energy-dependent arsenite exclusion. Exclusion of 73 AsO 2 ؊ from cells expressing only the arsB gene was coupled to electrochemical energy, while in cells expressing both genes, transport was coupled to chemical energy, most likely ATP. These results suggest that the Ars anion transport system can be either an obligatory ATP-coupled primary pump or a secondary carrier coupled to the proton motive force, depending on the subunit composition of the transport complex.Bacterial resistance to arsenical and antimonial compounds results from active extrusion of the toxic oxyanions from the resistant cells (15). Efflux of arsenite from oxyanion resistant Escherichia coli cells is catalyzed by a pump whose genes are encoded on the conjugative R factor R773 (5, 10). This aniontranslocating ATPase is composed of two types of polypeptides subunits, the ArsA and ArsB proteins. The 63-kDa ArsA protein is an anion-stimulated ATPase (11, 23) that functions as the catalytic component of the pump and remains attached to the inner membrane through interaction with the ArsB subunit (7, 30). The ArsB polypeptide is a 45-kDa inner membrane protein (26) that presumably forms the anion-conducting pathway.In vivo chemical energy was shown to be both necessary and sufficient for the pump, while electrochemical energy was neither (18,22). These studies were performed with an unc strain of E. coli defective in the H ϩ -translocating ATPase that catalyzes the equilibrium between ATP and the electrochemical proton gradient. This allows the establishment of intracellular conditions such that either chemical energy or electrochemical energy is available for transport (2). While the identity of the chemical used for energy coupling cannot be determined from the in vivo results, the energy requirement in vitro was similarly linked to chemical energy. In everted membrane vesicles, ATP was specifically required for uptake of arsenite, while electrochemical energy was neither necessary nor sufficient (6). Thus, the R773 ArsA-ArsB complex is clearly an obligatorily ATPcoupled pump.Similar arsenite resistance operons have been identified in plasmids of the gram-positive bacteria Staphylococcus aureus(pI258) (12) and Staphylococcus xylosus(pSX267) (24). The staphylococcal ars operons do not contain an arsA gene, yet the resistant cells still actively extrude arsenite (27,28), suggesting that the ArsB protein can transport arsenite in the absence of an arsA gene product. It is possible that the cells use a chromosomally encoded ATPase as a replacement for the ArsA protein or t...

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confidence: 99%

Dual mode of energy coupling by the oxyanion-translocating ArsB protein

1995

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“…The resulting 89-90 kDa size of this cross-reactive fraction is the size expected for dimerization of the ArsB protein. The ArsA protein is known to exist as a homodimer that is catalytically active [14] and a trimeric form in solution with arsenite [35]. The effects of arsenite Fig.…”

Section: Exclusion Chromatographymentioning

confidence: 99%

“…The arsA and arsB gene products are suffi cient for resistance to arsenite and antimonite and function as an effi cient anion pump (an arsenite-translocating ATPase) [14]. Although the arsB gene product alone will provide resistance to these two metalloids, the presence of the ArsA increases the level of resistance [15].…”

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confidence: 99%

Construction and purification of His-tagged staphylococcal ArsB protein, an integral membrane protein that is involved in arsenical salt resistance

2009

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Bacterial resistance to arsenical salts encoded on plasmid pI258 occurs by active extrusion of toxic oxyanions from cells of Staphylococcus aureus. The operon encodes for three gene products: ArsR, ArsB and ArsC. The gene product of arsB is an integral membrane protein and it is suffi cient to provide resistance to arsenite and antimonite. A poly His-ArsB fusion protein was generated to purify the staphylococcal ArsB protein. Cells containing the His-tagged arsB gene were resistant to arsenite and antimonite. The levels of resistance to these toxic oxyanions by the His-tagged construct were greater than the levels obtained with the wild type gene. These data would indicate that the His-tagged protein is functionally active. A new 36 kDa protein band was visualized on 10% SDS-polyacrylamide gel electrophoresis (PAGE), which was confi rmed as the His-ArsB protein by immunodetection with polyclonal Hisantibodies. The His-ArsB fusion protein was purifi ed by the use of metal-chelate affi nity chromatography with a Ni +2 -nitrilotriacetic acid column and size-exclusion chromatography suggests that the protein was a homodimer.

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“…These genes are often plasmid-encoded and are widespread in prokaryotes (Bruhn et al, 1996;Ji & Silver, 1992b;Oden et al, 1994;Rosenstein et al, 1992). In thoroughly studied systems, the ars operon has been reported to contain the five genes arsRDABC, as in Escherichia coli (Cai & DuBow, 1996;Rosen et al, 1992), or at least the three genes arsRBC, as in Staphylococcus aureus (Silver et al, 1993). ArsA and ArsB are components of an arsenite-transporting ATPase, where ArsA is the ATPase and ArsB is the transmembrane component of the complex.…”

Section: Introductionmentioning

confidence: 99%

“…3). Sequences belonging to the ArsC family, first described in E. coli (Kaur & Rosen, 1992;Silver et al, 1981), rely on reducing equivalents from glutathione (GSH) and are characterized by a thioredoxin (TRX) fold domain, a motif also found in thioredoxins and glutaredoxins. Because this family of reductases requires glutaredoxin to reduce arsenate, we used the GK genome as a guide and examined the region surrounding the ars operons and arsC3 in the GK annotation.…”

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Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1

et al. 2011

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Geobacillus kaustophilus strain A1 was previously isolated from a geothermal environment for its ability to grow in the presence of high arsenate levels. In this study, the molecular mechanisms of arsenate resistance of the strain were investigated. As(V) was reduced to As(III), as shown by HPLC analysis. Consistent with the observation that the micro-organism is not capable of anaerobic growth, no respiratory arsenate reductases were identified. Using specific PCR primers based on the genome sequence of G. kaustophilus HTA426, three unlinked genes encoding detoxifying arsenate reductases were detected in strain A1. These genes were designated arsC1, arsC2 and arsC3. While arsC3 is a monocistronic locus, sequencing of the regions flanking arsC1 and arsC2 revealed the presence of additional genes encoding a putative arsenite transporter and an ArsR-like regulator upstream of each arsenate reductase, indicating the presence of sequences with putative roles in As(V) reduction, As(III) export and arsenic-responsive regulation. RT-PCR demonstrated that both sets of genes were co-transcribed. Furthermore, arsC1 and arsC2, monitored by quantitative real-time RT-PCR, were upregulated in response to As(V), while arsC3 was constitutively expressed at a low level. A mechanism for regulation of As(V) detoxification by Geobacillus that is both consistent with our findings and relevant to the biogeochemical cycle of arsenic and its mobility in the environment is proposed. INTRODUCTIONMicro-organisms have an important impact on the biogeochemical transformations of arsenic, and their activities affect the mobility and toxicity of this element. Elevated amounts of arsenic can occur, especially in geothermal environments (Stauffer & Thompson, 1984). Thus, thermophilic micro-organisms such as Geobacillus species that thrive in geothermal soils and sediments are of particular interest for studying the mechanisms for the detoxification of arsenic compounds.Genes for arsenic detoxification were first discovered and characterized in Gram-negative bacteria (Chen et al., 1986;Rosen, 1999). These genes are often plasmid-encoded and are widespread in prokaryotes (Bruhn et al., 1996;Ji & Silver, 1992b;Oden et al., 1994;Rosenstein et al., 1992). In thoroughly studied systems, the ars operon has been reported to contain the five genes arsRDABC, as in Escherichia coli (Cai & DuBow, 1996;Rosen et al., 1992), or at least the three genes arsRBC, as in Staphylococcus aureus (Silver et al., 1993). ArsA and ArsB are components of an arsenite-transporting ATPase, where ArsA is the ATPase and ArsB is the transmembrane component of the complex. In micro-organisms in which ArsA is absent, ArsB acts as a single-component transporter. Both ArsA and ArsB may confer resistance to arsenite and antimonite (Rosen, 1999). In its dimeric form, ArsR is an arsenite-responsive repressor that binds to the ars promoter (Xu & Rosen, 1997). ArsC is the arsenate reductase that converts arsenate to arsenite, conferring resistance to arsenate (Martin et al., 2001 Here w...

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Plasmid-encoded resistance to arsenic and antimony

Cited by 106 publications

References 60 publications

Dual mode of energy coupling by the oxyanion-translocating ArsB protein

Dual mode of energy coupling by the oxyanion-translocating ArsB protein

Construction and purification of His-tagged staphylococcal ArsB protein, an integral membrane protein that is involved in arsenical salt resistance

Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1

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