Zn2+-sensing by the cyanobacterial metallothionein repressor SmtB: different motifs mediate metal-induced protein-DNA dissociation
| Autor: | Jennifer S. Turner, Nigel J. Robinson, Anthony C. R. Samson, Paul D. Glands |
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| Rok vydání: | 1996 |
| Předmět: |
Operator Regions
Genetic Molecular Sequence Data Mutant Repressor lac operon Biology Cyanobacteria DNA-binding protein chemistry.chemical_compound Bacterial Proteins Transcription (biology) Escherichia coli Genetics Metallothionein Amino Acid Sequence Cloning Molecular Promoter Regions Genetic Gene Sequence Homology Amino Acid Recombinant Proteins DNA-Binding Proteins Repressor Proteins Zinc Biochemistry chemistry Mutagenesis DNA Protein Binding Research Article |
| Zdroj: | Nucleic Acids Research. 24:3714-3721 |
| ISSN: | 1362-4962 |
| DOI: | 10.1093/nar/24.19.3714 |
| Popis: | SmtB is a member of a family of repressors which dissociate from DNA in the presence of metals; Zn2+ being the most potent inducer of metallothionein gene (smtA) transcription in vivo. In Synechococcus PCC 7942 cells devoid of chromosomal smtB, four plasmid-encoded mutants of SmtB (C61S, T11S/C14S, C121S and H105R/H106R) repressed lacZ expression driven by the smtA operator-promoter. Gel retardation assays with extracts from the complemented cells detected multiple SmtB-dependent complexes similar to those obtained with extracts from wild-type cells or with recombinant-SmtB. Elevated [Zn2+] alleviated repression in vivo by all of the mutants except H105R/H106R. These His residues (one or both) are therefore essential for Zn2+-sensing while, contrary to expectations, Cys residues are not. Hence different motifs facilitate metal-induced DNA-dissociation by SmtB and ArsR (the related oxyanion-sensing repressor), presumably generating variety in the spectra of metals sensed. Nucleotides and amino acids involved in DNA-SmtB interaction have been further defined/inferred and we also confirm that additional unknown factors form specific associations with the smt operator-promoter in elevated [Zn2+]. |
| Databáze: | OpenAIRE |
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