Structural highlights
Function
[SMTB_SYNE7] Transcriptional repressor of the expression of the smtA gene. Binds two zinc ions per dimer. The complex of DNA and SmtB is dissociated by zinc ions.[1] [2] [3]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
SmtB from Synechococcus PCC7942 is a trans-acting dimeric repressor that is required for Zn(2+)-responsive expression of the metallothionein SmtA. The structure of SmtB was solved using multiple isomorphous replacement techniques and refined at 2.2 A resolution by simulated annealing to an R-factor of 0.218. SmtB displays the classical helix-turn-helix motif found in many DNA-binding proteins. It has an alpha + beta topology, and the arrangement of the three core helices and the beta hairpin is similar to the HNF-3/fork head, CAP and diphtheria toxin repressor proteins. Although there is no zinc in the crystal structure, analysis of a mercuric acetate derivative suggests a total of four Zn2+ binding sites in the dimer. Two of these putative sites are at the opposite ends of the dimer, while the other two are at the dimer interface and are formed by residues contributed from each monomer. The structure of the dimer is such that simultaneous binding for both recognition helices to DNA would require either a bend in the DNA helix or a conformational change in the dimer. The structure of Synechococcus SmtB is the first in this family of metal-binding DNA repressors.
Crystal structure of the cyanobacterial metallothionein repressor SmtB: a model for metalloregulatory proteins.,Cook WJ, Kar SR, Taylor KB, Hall LM J Mol Biol. 1998 Jan 16;275(2):337-46. PMID:9466913[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ VanZile ML, Chen X, Giedroc DP. Allosteric negative regulation of smt O/P binding of the zinc sensor, SmtB, by metal ions: a coupled equilibrium analysis. Biochemistry. 2002 Aug 6;41(31):9776-86. PMID:12146943
- ↑ Morita EH, Wakamatsu M, Uegaki K, Yumoto N, Kyogoku Y, Hayashi H. Zinc ions inhibit the protein-DNA complex formation between cyanobacterial transcription factor SmtB and its recognition DNA sequences. Plant Cell Physiol. 2002 Oct;43(10):1254-8. PMID:12407207
- ↑ Turner JS, Glands PD, Samson AC, Robinson NJ. Zn2+-sensing by the cyanobacterial metallothionein repressor SmtB: different motifs mediate metal-induced protein-DNA dissociation. Nucleic Acids Res. 1996 Oct 1;24(19):3714-21. PMID:8871549
- ↑ Cook WJ, Kar SR, Taylor KB, Hall LM. Crystal structure of the cyanobacterial metallothionein repressor SmtB: a model for metalloregulatory proteins. J Mol Biol. 1998 Jan 16;275(2):337-46. PMID:9466913 doi:10.1006/jmbi.1997.1443
