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Nucleic Acids Res. 1993 February 25; 21(4): 921–925.
PMCID: PMC309225

SmtB is a metal-dependent repressor of the cyanobacterial metallothionein gene smtA: identification of a Zn inhibited DNA-protein complex.

Abstract

The smt locus of Synechococcus PCC 7942 contains a metal-regulated gene (smtA), which encodes a class II metallothionein, and a divergently transcribed gene, smtB, which encodes a repressor of smtA transcription. Regions containing cis-acting elements required for efficient induction, and required for smtB-dependent repression, of the smtA operator-promoter were identified. Specific interactions between proteins extracted from Synechococcus PCC 7942 and defined regions surrounding the smtA operator-promoter were detected by electrophoretic mobility shift assays. Three metallothionein operator-promoter associated complexes were identified, one of which (MAC1) showed Zn-dependent dissociation and involved a region of DNA immediately upstream of smtA. Treatment with Zn-chelators facilitated re-association of MAC1 in vitro. MAC1 was not observed in extracts from smt deficient mutants but was restored in extracts from mutants complemented with a plasmid borne smtB. SmtB is thus required for the formation of a Zn-responsive complex with the smt operator-promoter and based upon the predicted structure of SmtB we propose direct SmtB-DNA interaction exerting metal-ion inducible negative control.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Thiele DJ. Metal-regulated transcription in eukaryotes. Nucleic Acids Res. 1992 Mar 25;20(6):1183–1191. [PMC free article] [PubMed]
  • Fürst P, Hu S, Hackett R, Hamer D. Copper activates metallothionein gene transcription by altering the conformation of a specific DNA binding protein. Cell. 1988 Nov 18;55(4):705–717. [PubMed]
  • Robinson NJ, Gupta A, Fordham-Skelton AP, Croy RR, Whitton BA, Huckle JW. Prokaryotic metallothionein gene characterication and expression: chromosome crawling by ligation-mediated PCR. Proc Biol Sci. 1990 Dec 22;242(1305):241–247. [PubMed]
  • Olafson RW, McCubbin WD, Kay CM. Primary- and secondary-structural analysis of a unique prokaryotic metallothionein from a Synechococcus sp. cyanobacterium. Biochem J. 1988 May 1;251(3):691–699. [PubMed]
  • Shi J, Lindsay WP, Huckle JW, Morby AP, Robinson NJ. Cyanobacterial metallothionein gene expressed in Escherichia coli. Metal-binding properties of the expressed protein. FEBS Lett. 1992 Jun 1;303(2-3):159–163. [PubMed]
  • Dodd IB, Egan JB. Improved detection of helix-turn-helix DNA-binding motifs in protein sequences. Nucleic Acids Res. 1990 Sep 11;18(17):5019–5026. [PMC free article] [PubMed]
  • San Francisco MJ, Hope CL, Owolabi JB, Tisa LS, Rosen BP. Identification of the metalloregulatory element of the plasmid-encoded arsenical resistance operon. Nucleic Acids Res. 1990 Feb 11;18(3):619–624. [PMC free article] [PubMed]
  • Ji G, Silver S. Regulation and expression of the arsenic resistance operon from Staphylococcus aureus plasmid pI258. J Bacteriol. 1992 Jun;174(11):3684–3694. [PMC free article] [PubMed]
  • Yoon KP, Silver S. A second gene in the Staphylococcus aureus cadA cadmium resistance determinant of plasmid pI258. J Bacteriol. 1991 Dec;173(23):7636–7642. [PMC free article] [PubMed]
  • Ivey DM, Guffanti AA, Shen Z, Kudyan N, Krulwich TA. The cadC gene product of alkaliphilic Bacillus firmus OF4 partially restores Na+ resistance to an Escherichia coli strain lacking an Na+/H+ antiporter (NhaA). J Bacteriol. 1992 Aug;174(15):4878–4884. [PMC free article] [PubMed]
  • Kondorosi E, Pierre M, Cren M, Haumann U, Buiré M, Hoffmann B, Schell J, Kondorosi A. Identification of NolR, a negative transacting factor controlling the nod regulon in Rhizobium meliloti. J Mol Biol. 1991 Dec 20;222(4):885–896. [PubMed]
  • van der Plas J, Hegeman H, de Vrieze G, Tuyl M, Borrias M, Weisbeek P. Genomic integration system based on pBR322 sequences for the cyanobacterium Synechococcus sp. PCC7942: transfer of genes encoding plastocyanin and ferredoxin. Gene. 1990 Oct 30;95(1):39–48. [PubMed]
  • Scanlan DJ, Bloye SA, Mann NH, Hodgson DA, Carr NG. Construction of lacZ promoter probe vectors for use in Synechococcus: application to the identification of CO2-regulated promoters. Gene. 1990 May 31;90(1):43–49. [PubMed]
  • Elborough KM, West SC. Specific binding of cruciform DNA structures by a protein from human extracts. Nucleic Acids Res. 1988 May 11;16(9):3603–3616. [PMC free article] [PubMed]
  • Devereux J, Haeberli P, Smithies O. A comprehensive set of sequence analysis programs for the VAX. Nucleic Acids Res. 1984 Jan 11;12(1 Pt 1):387–395. [PMC free article] [PubMed]
  • Vallee BL, Coleman JE, Auld DS. Zinc fingers, zinc clusters, and zinc twists in DNA-binding protein domains. Proc Natl Acad Sci U S A. 1991 Feb 1;88(3):999–1003. [PubMed]

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