Zn2+-sensing by the cyanobacterial metallothionein repressor SmtB: different motifs mediate metal-induced protein-DNA dissociation

Turner, Jennifer S.; Glands, Paul D.; Samson, A. C. R.; Robinson, Nigel J.

doi:10.1093/nar/24.19.3714

Cited by 87 publications

(105 citation statements)

References 29 publications

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“…CzrA was homologous to the SmtB in Synechococcus PCC7942, CadC of pI258 and ArsR of p1258 in S. aureus (13,36,40,44). SmtB, ArsR and CadC contained helix-turn-helix DNA binding motifs and are assumed to be the repressors for smtA (methalothionein), arsABC (arsenate and antimony transport system proteins) and CadA (cadmium transport system), respectively.…”

Section: Discussionmentioning

confidence: 99%

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Chromosome‐Determined Zinc‐Responsible Operon czr in Staphylococcus aureus Strain 912

Kuroda

Hayashi

Ohta

1999

Microbiology and Immunology

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A novel operon, czrAB (zinc-responsible genes), was identified in the chromosome of Staphylococcus aureus. The operon consists of two genes, czrA and czrB. The czrA gene, coding for an 11.5 kDa protein, was homologous to cadC, arsR of S. aureus plasmid pI258 and smtB of Synechococcus PCC7942. The czrB, coding for a 36 kDa membrane spanning protein, was homologous to the czcD gene, cobalt, zinc and the cadmium-resistant factor of Bacillus subtilis and Alcaligenes eutrophus. In the presence of zinc (0.1-10 mM), the transcription of czrAB was enhanced in a concentration-dependent manner. Other heavy metals, such as cobalt, copper, manganese and nickel showed no effect on czrAB expression. The disruptant of the czrB gene became sensitive to zinc ion (MIC, 2 mM; MBC, 10 mM), and the complementation with the plasmid recovered the resistance to zinc at the same concentration as a parental strain (MIC, 5 mM; MBC, 20 mM). The disruptant accumulated intracellular zinc up to 0.4 mg per g dry weight of the organism, while that of the parental strain was 0.25 mg per g dry weight. The findings indicated that the novel operon czrAB should play a role in the transportation of zinc across the cell membrane to maintain the proper intracellular concentration.

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Section: Discussionmentioning

confidence: 99%

“…3A) (7). The amino acid sequence for czrA exhibited 34.5% amino acid identities with SmtB in Synechococcus PCC7942, 31.2% CadC of pI258 in S. aureus, and 25.6% ArsR of pI258 in S. aureus (13, 40,44).…”

Section: Chromosomal Czr Operon In S Aureusmentioning

confidence: 99%

Chromosome‐Determined Zinc‐Responsible Operon czr in Staphylococcus aureus Strain 912

Kuroda

Hayashi

Ohta

1999

Microbiology and Immunology

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“…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 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).…”

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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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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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“…Gel Retardation Assays-Assays were performed with 0.5 mM spermidine in the binding buffer as described previously (26). Samples were loaded onto 5% polyacrylamide gels and electrophoresed using Trisborate-EDTA (19) buffer.…”

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confidence: 99%

Cobalt-dependent Transcriptional Switching by a Dual-effector MerR-like Protein Regulates a Cobalt-exporting Variant CPx-type ATPase

Rutherford¹,

Cavet

Robinson

1999

Journal of Biological Chemistry

116

151

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CoaR associates with and confers cobalt-dependent activation of the coaT operator-promoter. A CoaR mutant (Ser-Asn-Ser) in a carboxyl-terminal Cys-His-Cys motif bound the coaT operator-promoter but did not activate expression in response to cobalt, implicating thiolate and/or imidazole ligands at these residues in an allosteric cobalt binding site. Deletion of 1 or 2 nucleotides from between near consensus, but with aberrant (20 base pairs) spacing, ؊10 and ؊35 elements enhanced expression from the coaT operator-promoter but abolished activation by cobalt-CoaR. It is inferred that cobalt effects a transition in CoaR that underwinds the coaT operator-promoter to realign promoter elements. In the absence of cobalt, CoaR represses expression (ϳ50%). CoaR is a fusion of ancestral MerR (mercuryresponsive transcriptional activator)-and precorrin isomerase (enzyme of vitamin B 12 biosynthesis)-related sequences.Expression from the coaT operator-promoter was enhanced in a partial mutant of cbiE (encoding an enzyme preceding precorrin isomerase in B 12 biosynthesis), revealing that this pathway "inhibits" coaT expression. Disruption of coaT reduced cobalt tolerance and increased cytoplasmic 57

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Zn2+-sensing by the cyanobacterial metallothionein repressor SmtB: different motifs mediate metal-induced protein-DNA dissociation

Cited by 87 publications

References 29 publications

Chromosome‐Determined Zinc‐Responsible Operon czr in Staphylococcus aureus Strain 912

Chromosome‐Determined Zinc‐Responsible Operon czr in Staphylococcus aureus Strain 912

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)

Cobalt-dependent Transcriptional Switching by a Dual-effector MerR-like Protein Regulates a Cobalt-exporting Variant CPx-type ATPase

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