Coordination Chemistry of Bacterial Metal Transport and Sensing

Ma, Zhen; Jacobsen, Faith E.; Giedroc, David P.

doi:10.1021/cr900077w

Cited by 555 publications

(576 citation statements)

References 411 publications

(1,474 reference statements)

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“…S4B). SqrR is a member of the arsenic repressor (ArsR) family of prokaryotic repressors (30), and is evolutionarily related to BigR from the plant pathogens Xyella and Agrobacterium spp., described previously as mediating hydrogen sulfide detoxification (31). An unrooted phylogenetic tree of SqrR homologs indicates that some β-and γ-proteobacterial SqrR homologs are found within the α-proteobacterial clade, suggesting lateral gene transfer of sqrR among proteobacteria (Fig.…”

Section: Resultsmentioning

confidence: 99%

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

Shimizu

Shen

Fang

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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113

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Sulfide was used as an electron donor early in the evolution of photosynthesis, with many extant photosynthetic bacteria still capable of using sulfur compounds such as hydrogen sulfide (H 2 S) as a photosynthetic electron donor. Although enzymes involved in H 2 S oxidation have been characterized, mechanisms of regulation of sulfide-dependent photosynthesis have not been elucidated. In this study, we have identified a sulfide-responsive transcriptional repressor, SqrR, that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus. SqrR has three cysteine residues, two of which, C41 and C107, are conserved in SqrR homologs from other bacteria. Analysis with liquid chromatography coupled with an electrospray-interface tandem-mass spectrometer reveals that SqrR forms an intramolecular tetrasulfide bond between C41 and C107 when incubated with the sulfur donor glutathione persulfide. SqrR is oxidized in sulfidestressed cells, and tetrasulfide-cross-linked SqrR binds more weakly to a target promoter relative to unmodified SqrR. C41S and C107S R. capsulatus SqrRs lack the ability to respond to sulfide, and constitutively repress target gene expression in cells. These results establish that SqrR is a sensor of H 2 S-derived reactive sulfur species that maintain sulfide homeostasis in this photosynthetic bacterium and reveal the mechanism of sulfide-dependent transcriptional derepression of genes involved in sulfide metabolism.sulfide sensor | photosynthesis regulation | reactive sulfur species | purple bacteria | Rhodobacter T he discovery of ∼550 deep-sea hydrothermal vents more than 30 y ago (1) has led to the theory that energy metabolism in early ancestral organisms may have arisen from deep-sea hydrothermal vents where simple inorganic molecules such as hydrogen sulfide or hydrogen gas, as well as methane, exist (2-4). Such ancient energy metabolism has been assumed to be similar to that of extant chemolithotrophs, which obtain energy from these molecules. Indeed, various chemolithoautotrophic microbes thrive in deep-sea hydrothermal vents and are capable of oxidizing sulfides, methane, and/or hydrogen gas for use as energy sources and electron donors (5). Some photosynthetic bacteria have also been isolated from deep-sea hydrothermal vents that can grow photosynthetically using sulfide as an electron donor and geothermal radiation as an energy source instead of solar radiation (6), as hypothesized for ancestral phototrophs.Many purple photosynthetic bacteria have remarkable metabolic versatility required to meet the energy demands of sulfidedependent and -independent photosynthesis as well as aerobic and anaerobic respiration. These bacteria tightly control the synthesis of their electron transfer proteins involved in each growth mode in response to a specific electron donor, oxygen tension, and light intensity (7, 8). Among these regulatory systems, oxygen-and lightsensing mechanisms have been well-studied; however, mechanisms used to sen...

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Section: Resultsmentioning

confidence: 99%

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

Shimizu

Shen

Fang

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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113

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“…metalloregulatory proteins [17] or metallothioneins [18]) or pre-designed oligopeptides fused to carrier proteins [14,15,[19][20][21][22][23] may be promising candidates in metal ion removal. Appropriate peptides [6,[24][25][26] or the highly efficient and selective bacterial metal responsive metalloregulatory proteins [27] are also utilized in the construction of biosensors [7,8,[28][29][30] for the detection of toxic metal ions. The applied sequences generally contain cysteines with a soft sulfur donor atom showing high affinity 4 towards the heavy metal ions.…”

Section: Introductionmentioning

confidence: 99%

Competition of zinc(II) with cadmium(II) or mercury(II) in binding to a 12-mer peptide

Jancsó

Gyurcsik

Mesterházy

et al. 2013

Journal of Inorganic Biochemistry

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“…Many others are required for cellular function, such as Zn and Cu, but can be toxic in excess. Cells have thus developed many ways to regulate intracellular metal concentrations (1)(2)(3)(4)(5)(6)(7)(8)(9). Metal-responsive transcriptional regulation is one of them, where metalloregulators respond to intracellular metal ions and regulate transcription of metal efflux, uptake, or other metal homeostasis genes (4)(5)(6)(7)(8)(9).…”

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confidence: 99%

Metalloregulator CueR biases RNA polymerase’s kinetic sampling of dead-end or open complex to repress or activate transcription

Martell

Joshi

Gaballa

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Metalloregulators respond to metal ions to regulate transcription of metal homeostasis genes. MerR-family metalloregulators act on σ 70 -dependent suboptimal promoters and operate via a unique DNA distortion mechanism in which both the apo and holo forms of the regulators bind tightly to their operator sequence, distorting DNA structure and leading to transcription repression or activation, respectively. It remains unclear how these metalloregulator−DNA interactions are coupled dynamically to RNA polymerase (RNAP) interactions with DNA for transcription regulation. Using single-molecule FRET, we study how the copper efflux regulator (CueR)-a Cu + -responsive MerR-family metalloregulator-modulates RNAP interactions with CueR's cognate suboptimal promoter PcopA, and how RNAP affects CueR−PcopA interactions. We find that RNAP can form two noninterconverting complexes at PcopA in the absence of nucleotides: a dead-end complex and an open complex, constituting a branched interaction pathway that is distinct from the linear pathway prevalent for transcription initiation at optimal promoters. Capitalizing on this branched pathway, CueR operates via a "biased sampling" instead of "dynamic equilibrium shifting" mechanism in regulating transcription initiation; it modulates RNAP's binding-unbinding kinetics, without allowing interconversions between the deadend and open complexes. Instead, the apo-repressor form reinforces the dominance of the dead-end complex to repress transcription, and the holo-activator form shifts the interactions toward the open complex to activate transcription. RNAP, in turn, locks CueR binding at PcopA into its specific binding mode, likely helping amplify the differences between apo-and holo-CueR in imposing DNA structural changes. Therefore, RNAP and CueR work synergistically in regulating transcription.single-molecule FRET | protein-DNA interaction dynamics | MerR-family regulators | metal-responsive transcription regulation M aintaining cellular metal homeostasis is essential for bacteria, which often dwell in environments with high concentrations of metals. Some of these metals are purely toxic to bacteria, such as Cd and Hg. Many others are required for cellular function, such as Zn and Cu, but can be toxic in excess. Cells have thus developed many ways to regulate intracellular metal concentrations (1-9). Metal-responsive transcriptional regulation is one of them, where metalloregulators respond to intracellular metal ions and regulate transcription of metal efflux, uptake, or other metal homeostasis genes (4-9).In Gram-negative bacteria, MerR-family metalloregulators act on σ 70 -dependent suboptimal promoters to repress or activate transcription of metal resistance genes (7,8). These suboptimal promoters have elongated spacing, 19-20 bp (Fig. 1), compared with the optimal 17 ± 1 bp, between the −35 and −10 elements. This elongated spacing causes a misalignment of these two recognition elements, impairing proper interactions with the RNA polymerase (RNAP) and leading to a weak basal leve...

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Coordination Chemistry of Bacterial Metal Transport and Sensing

Cited by 555 publications

References 411 publications

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

Competition of zinc(II) with cadmium(II) or mercury(II) in binding to a 12-mer peptide

Metalloregulator CueR biases RNA polymerase’s kinetic sampling of dead-end or open complex to repress or activate transcription

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