A periplasmic arsenite‐binding protein involved in regulating arsenite oxidation

Liu, Guanghui; Liu, Mengyao; Kim, Eun Hae; Maaty, Walid S.; Bothner, Brian; Lei, Benfang; Rensing, Christopher; Wang, Gejiao; McDermott, Timothy R.

doi:10.1111/j.1462-2920.2011.02672.x

Cited by 81 publications

(83 citation statements)

References 48 publications

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“…Soon thereafter, and in part stimulated by the massive arsenic poisoning disaster in Bangladesh (2), a series of studies initiated the characterization of microbial As III oxidation in natural environments, including geothermal springs (9,11,12,17,19,24,25,35,51) and soils (41); in mining-contaminated environments (6,13,40); and, most recently, in anoxic photosynthesis (21,33 (28,31) indicated the role and importance of the sensor kinase AioS and its putative regulatory partner AioR (a bacterial enhancer binding protein), direct proof of these two proteins working together as part of a putative As III signal perception and transduction cascade was just recently provided by Sardiwal et al (54), who demonstrated the autophosphorylation of an AioS component and the AioS-specific phosphorylation of AioR. Recently, our work has expanded this regulatory model to now include a third component, AioX, which is a periplasmic As III binding protein that is also essential for aioBA expression (39 …”

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Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Kang

Bothner

Rensing

et al. 2012

Appl Environ Microbiol

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In this study with the model organism Agrobacterium tumefaciens, we used a combination of lacZ gene fusions, reverse transcriptase PCR (RT-PCR), and deletion and insertional inactivation mutations to show unambiguously that the alternative sigma factor RpoN participates in the regulation of As III oxidation. A deletion mutation that removed the RpoN binding site from the aioBA promoter and an aacC3 (gentamicin resistance) cassette insertional inactivation of the rpoN coding region eliminated aioBA expression and As III oxidation, although rpoN expression was not related to cell exposure to As III . Putative RpoN binding sites were identified throughout the genome and, as examples, included promoters for aioB, phoB1, pstS1, dctA, glnA, glnB, and flgB that were examined by using qualitative RT-PCR and lacZ reporter fusions to assess the relative contribution of RpoN to their transcription. The expressions of aioB and dctA in the wild-type strain were considerably enhanced in cells exposed to As III , and both genes were silent in the rpoN::aacC3 mutant regardless of As III . The expression level of glnA was not influenced by As III but was reduced (but not silent) in the rpoN::aacC3 mutant and further reduced in the mutant under N starvation conditions. The rpoN::aacC3 mutation had no obvious effect on the expression of glnB, pstS1, phoB1, or flgB. These experiments provide definitive evidence to document the requirement of RpoN for As III oxidation but also illustrate that the presence of a consensus RpoN binding site does not necessarily link the associated gene with regulation by As III or by this sigma factor. E vidence of microbial arsenite (As III ) oxidation was first reported nearly a century ago (18). Subsequent progress has been sporadic, with work that identified some organisms capable of As III oxidation (46,48,60) and then a study of a Pseudomonas arsenitoxidans strain reported to grow chemolithoautotrophically with As III as a sole electron donor (23). Subsequent follow-up characterizations of this organism and this process failed to materialize; however, approximately 2 decades later, Santini et al. (52) described the isolation and initial characterization of a Rhizobiumlike bacterium (strain NT-26) that could grow chemolithoautotrophically with As III as a sole electron donor for energy generation and with CO 2 as a sole carbon source. Soon thereafter, and in part stimulated by the massive arsenic poisoning disaster in Bangladesh (2), a series of studies initiated the characterization of microbial As III oxidation in natural environments, including geothermal springs (9,11,12,17,19,24,25,35,51) and soils (41); in mining-contaminated environments (6, 13, 40); and, most recently, in anoxic photosynthesis (21, 33). Likewise, progress has been made in the understanding of the biochemistry of the As III oxidase enzyme (1,14,37 oxidase structural genes were later cloned from the above-mentioned Rhizobium NT-26 organism (53). The symbols for genes coding for functions associated with As III oxidation have...

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confidence: 98%

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

Kang

Bothner

Rensing

et al. 2012

Appl Environ Microbiol

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“…However, no or only one cysteine residue is present within the putative sensory domain of AioS. It was recently shown in A. tumefaciens that the protein that binds As(III) is, in fact, AioX, and it was proposed that this binding results in a conformational change of AioX, allowing its interaction with AioS (9).…”

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“…They must therefore delicately balance arsenic intracellular trafficking by controlling the expression of the genes involved in these mechanisms. Until now, only three regulators have been proposed to be involved in arsenic sensing: the ArsR and ArsD repressors and the three-component As(III) binding protein/sensor/regulator signal transduction system AioXSR (2,9,10). ArsR and ArsD act together to repress the basal and maximal levels of expression of the arsenical resistance ars operon of the Escherichia coli R773 plasmid.…”

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An ArsR/SmtB Family Member Is Involved in the Regulation by Arsenic of the Arsenite Oxidase Operon in Thiomonas arsenitoxydans

Moinier

Slyemi

Byrne

et al. 2014

Appl Environ Microbiol

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The genetic organization of the aioBA operon, encoding the arsenite oxidase of the moderately acidophilic and facultative chemoautotrophic bacterium Thiomonas arsenitoxydans, is different from that of the aioBA operon in the other arsenite oxidizers, in that it encodes AioF, a metalloprotein belonging to the ArsR/SmtB family. AioF is stabilized by arsenite, arsenate, or antimonite but not molybdate. Arsenic is tightly attached to AioF, likely by cysteine residues. When loaded with arsenite or arsenate, AioF is able to bind specifically to the regulatory region of the aio operon at two distinct positions. In Thiomonas arsenitoxydans, the promoters of aioX and aioB are convergent, suggesting that transcriptional interference occurs. These results indicate that the regulation of the aioBA operon is more complex in Thiomonas arsenitoxydans than in the other aioBA containing arsenite oxidizers and that the arsenic binding protein AioF is involved in this regulation. On the basis of these data, a model to explain the tight control of aioBA expression by arsenic in Thiomonas arsenitoxydans is proposed.

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“…Complementation of an aioR::Tn5B22 mutant [As(III) oxidation minus] required the entire aio region, indicating genes in the aio operon are part of a common transcriptional unit (7). Thus far, it appears that there are at least two separate regulatory circuits controlling the expression of the aio operon: (i) a twocomponent signal transduction system, AioS and AioR, which recently has been shown to include AioX as a putative periplasmic signal receptor (8); and (ii) quorum sensing, which is normally involved in virulence of plants (2,5), is also involved in regulating As(III) oxidation in A. tumefaciens 5A (7).…”

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“…We report the draft genome of the arsenite [As(III)]-oxidizing A. tumefaciens strain 5A isolated from an As-enriched Typic Calciaquoll soil collected from an irrigated pasture in the Madison River Valley, MT (9). Complex regulation of arsenite oxidation, including As(III)-sensing, three-component signal transduction, and quorum sensing are involved (7,8). Prior to this genome report, only a single A. tumefaciens whole-genome sequence (strain C58) had been published (4).…”

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