Metalloregulation of the cyanobacterial<i>smt</i>locus: indentification of SmtB binding sites and direct interaction with metals

Erbe, Jarrod L.; Taylor, Kenneth B.; Hall, Leo M.

doi:10.1093/nar/23.13.2472

Cited by 66 publications

(74 citation statements)

References 20 publications

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“…4, A and B, lane 10), revealing that the binding is indeed sequencespecific. Although the BxmR-DNA binding stoichiometry in C1, C2, and C3 is unknown and any linkage to the BxmR monomerdimer equilibrium (33) was not investigated in these experiments, these gel mobility shift patterns bear a qualitative resemblance to those published previously for apoSmtB from Synechococcus PCC7942 where up to four dimers are known to bind to a single 12-2-12 inverted repeat, two with high affinity (27,45,48).…”

Section: Bxmr Specifically Binds To the 12-2-12 Inverted Repeat Elemementioning

confidence: 53%

“…In prokaryotes, the expression of these genes is tightly controlled by specific metalloregulators or "metal-sensing" transcriptional regulators (12,24,25). One such family of homologous metal sensor proteins is the SmtB/ArsR family, named for Synechococcus PCC7942 SmtB, a Zn(II)-responsive transcriptional repressor (26,27) that negatively regulates the transcription of SmtA, a cyanobacterial metallothionein (13,23), and Escherichia coli R773-encoded ArsR, an As(III)/Sb(III) regulator of the ars operon (28,29). Other members include Staphylococcus aureus pI258 CadC (30,31) and S. aureus CzrA (32,33) that regulate the expression of a metal-transporting CPx-ATPase (CadA) and a cation-facilitated diffusion antiporter (CzrB), respectively.…”

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confidence: 99%

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A Novel Cyanobacterial SmtB/ArsR Family Repressor Regulates the Expression of a CPx-ATPase and a Metallothionein in Response to Both Cu(I)/Ag(I) and Zn(II)/Cd(II)

Liu

Nakashima

Hirose

et al. 2004

Journal of Biological Chemistry

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A novel SmtB/ArsR family metalloregulator, denoted BxmR, has been identified and characterized from the cyanobacterium Oscillatoria brevis. Genetic and biochemical evidence reveals that BxmR represses the expression of both bxa1, encoding a CPx-ATPase metal transporter, as well as a divergently transcribed operon encoding bxmR and bmtA, a heavy metal sequestering metallothionein. Derepression of the expression of all three genes is mediated by both monovalent (Ag(I) and Cu(I)) and divalent (Zn(II) and Cd(II)) heavy metal ions, a novel property among SmtB/ArsR metal sensors. Electrophoretic gel mobility shift experiments reveal that apoBxmR forms multiple resolvable complexes with oligonucleotides containing a single 12-2-12 inverted repeat derived from one of the two operator/promoter regions with similar apparent affinities. Preincubation with either monovalent or divalent metal ions induces disassembly of both the BxmR-bxa1 and BxmR-bxmR/ bmtA operator/promoter complexes. Interestingly, the temporal regulation of expression of bxa1 and bmtA mRNAs is different in O. brevis with bxa1 induced first upon heavy metal treatment, followed by bmtA/bxmR. A dynamic interplay among Bxa1, BmtA, and BxmR is proposed that maintains metal homeostasis in O. brevis by balancing the relative rates of metal storage and efflux of multiple heavy metal ions.Transition metal ions such as zinc, copper, iron, and manganese are essential trace elements that play integral catalytic functions in myriad metalloenzymes and electron transfer in all organisms (1-3). However, they are required only in trace amounts and, when present in excess in the environment, even essential metals can be cytotoxic, like heavy metal pollutants (4 -6). All organisms have evolved a range of mechanisms that govern metal homeostasis, defined as maintaining the intracellular bioavailable concentrations of essential metal ions within a range compatible with cell viability (7-9). Multiple lines of evidence from the past decade reveal that heavy metal homeostasis is maintained in all organisms by a small number of critical processes that include metal sensing, chelation, and transport (10 -18).Two distinct mechanisms play prominent roles in governing metal ion homeostasis and resistance in many organisms. One involves the uptake or efflux of specific heavy metal ions across biomembranes, mediated by ATP-coupled high affinity metal ion transporters such as those derived from the CPx-ATPase family (19 -21). Another mechanism involves the specific chelation of metal ions by intracellular chelators, e.g. metallothioneins (MTs), 1 now known to be widely distributed in nature (13,22,23). To meet the diverse biological requirements of specific metal ions, various strategies have evolved to regulate the transcription of genes encoding these heavy metal homeostasis proteins. In prokaryotes, the expression of these genes is tightly controlled by specific metalloregulators or "metal-sensing" transcriptional regulators (12,24,25). One such family of homologous metal sensor pro...

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Section: Bxmr Specifically Binds To the 12-2-12 Inverted Repeat Elemementioning

confidence: 53%

mentioning

confidence: 99%

A Novel Cyanobacterial SmtB/ArsR Family Repressor Regulates the Expression of a CPx-ATPase and a Metallothionein in Response to Both Cu(I)/Ag(I) and Zn(II)/Cd(II)

Liu

Nakashima

Hirose

et al. 2004

Journal of Biological Chemistry

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“…The SmtB protein, which represses metallothionein expression in the cyanobacterium Synechococcus sp. strain PCC7942, is a helix-turn-helix protein whose DNA binding ability is inhibited by zinc binding to the protein (8,22). Zinc-induced expression of metallothionein genes in mammals involves the binding of one or more metal-responsive transcription factors (e.g., MTF-1 or ZRF) to sites (metal-regulated enhancer elements) in the metallothionein gene promoters (21,34).…”

Section: Discussionmentioning

confidence: 99%

Zap1p, a Metalloregulatory Protein Involved in Zinc-Responsive Transcriptional Regulation in Saccharomyces cerevisiae

Zhao

Eide

1997

Molecular and Cellular Biology

251

260

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Zinc ion homeostasis in Saccharomyces cerevisiae is controlled primarily through the transcriptional regulation of zinc uptake systems in response to intracellular zinc levels. A high-affinity uptake system is encoded by the ZRT1 gene, and its expression is induced more than 30-fold in zinc-limited cells. A low-affinity transporter is encoded by the ZRT2 gene, and this system is also regulated by zinc. We used a genetic approach to isolate mutants whose ZRT1 expression is no longer repressed in zinc-replete cells, and a new gene, ZAP1, was identified. ZAP1 encodes a 93-kDa protein with sequence similarity to transcriptional activators; the C-terminal 174 amino acids contains five C 2 H 2 zinc finger domains, and the N terminus (residues 1 to 706) has two potential acidic activation domains. The N-terminal region also contains 12% histidine and cysteine residues. The mutant allele isolated, ZAP1-1 up , is semidominant and caused high-level expression of ZRT1 and ZRT2 in both zinc-limited and zinc-replete cells. This phenotype is the result of a mutation that substitutes a serine for a cysteine residue in the N-terminal region. A zap1 deletion mutant grew well on zinc-replete media but poorly on zinc-limiting media. This mutant had low-level ZRT1 and ZRT2 expression in zinc-limited as well as zinc-replete cells. These data indicate that Zap1p plays a central role in zinc ion homeostasis by regulating transcription of the zinc uptake system genes in response to zinc. Finally, we present evidence that Zap1p regulates transcription of its own promoter in response to zinc through a positive autoregulatory mechanism.Zinc is essential for all organisms. This metal is a catalytic component of over 300 enzymes, including alcohol dehydrogenase, carbonic anhydrase, and carboxypeptidases (33). Zinc also plays a structural role in many proteins. For example, several motifs found in transcriptional regulatory proteins are stabilized by zinc, including the zinc finger, zinc cluster, and RING finger domains (28). Proteins containing these domains are very common; as many as 1% of all human gene products contain the C 2 H 2 zinc finger motif first identified in transcription factor IIIA (TFIIIA) (18).Although it is essential for many different cellular functions, zinc can also be toxic. When the intracellular zinc level rises to some critical level, the metal can interfere with vital processes, perhaps by competing with other metal ions for enzyme active sites, transporter proteins, and other biologically important ligands. The delicate balance of intracellular zinc is accomplished through precise homeostatic regulation mediated by a number of mechanisms. These include binding of the metal by cytoplasmic macromolecules such as metallothioneins (14) and phytochelatins (27), zinc storage in intracellular compartments (3,20,25), and transport of the metal out of the cell (26).The primary control point for zinc ion homeostasis is the regulation of zinc uptake across the plasma membrane. Little is known about the mechanism and regulat...

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“…In both Grampositive and Gram-negative bacteria the ars operons from Escherichia coli (Mobley et al 1983;Saltikov & Olson 2002) and Staphylococcus strains (Ji & Silver 1992;Rosenstein et al 1992), and the mer systems from Escherichia coli (Nascimento & Chartone-Souza 2003) and Bacillus populations (Bogdanova et al 1998) have been well characterized. In addition, the cyanobacterial smt locus from Synechococcus PCC 7942 also contains a well-characterized heavy metal resistance system (Erbe et al 1995).…”

Section: Introductionmentioning

confidence: 99%

The isolation of heavy-metal resistant culturable bacteria and resistance determinants from a heavy-metal-contaminated site

et al. 2010

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In this study we performed a phylogenetic analysis of a culturable bacterial community isolated from heavymetal-contaminated soil from southwest Slovakia using 16S rRNA (16S rDNA) and heavy-metal resistance genes. The soil sample contained high concentrations of nickel (2,109 mg/kg), cobalt (355 mg/kg) and zinc (177 mg/kg), smaller concentrations of iron (35.75 mg/kg) and copper (32.2 mg/kg), and a trace amount of cadmium (<0.25 mg/kg). A total of 100 isolates were grown on rich (Nutrient agar No. 2) or minimal (soil-extract agar medium) medium. The isolates were identified by phylogenetic analysis using partial sequences of their 16S rRNA (16S rDNA) genes. Representatives of two broad taxonomic groups, Firmicutes and Proteobacteria, were found on rich medium, whereas four taxonomic groups, Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria, were represented on minimal medium. Forty-two isolates grown on rich medium were assigned to 20 bacterial species, while 58 bacteria grown on minimal medium belonged to 49 species. Twenty-three isolates carried czcA-and/or nccA-like heavy-metal-resistance determinants. The heavy-metalresistance genes of nine isolates were identified by phylogenetic analysis of their protein sequences.

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Metalloregulation of the cyanobacterialsmtlocus: indentification of SmtB binding sites and direct interaction with metals

Cited by 66 publications

References 20 publications

A Novel Cyanobacterial SmtB/ArsR Family Repressor Regulates the Expression of a CPx-ATPase and a Metallothionein in Response to Both Cu(I)/Ag(I) and Zn(II)/Cd(II)

A Novel Cyanobacterial SmtB/ArsR Family Repressor Regulates the Expression of a CPx-ATPase and a Metallothionein in Response to Both Cu(I)/Ag(I) and Zn(II)/Cd(II)

Zap1p, a Metalloregulatory Protein Involved in Zinc-Responsive Transcriptional Regulation in Saccharomyces cerevisiae

The isolation of heavy-metal resistant culturable bacteria and resistance determinants from a heavy-metal-contaminated site

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