Structural highlights
Function
[SMTB_SYNP7] 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
The origin of metal ion selectivity by members of the SmtB/ArsR family of bacterial metal-sensing transcriptional repressors and the mechanism of negative allosteric regulation of DNA binding is poorly understood. Here, we report that two homologous zinc sensors, Staphylococcus aureus CzrA and cyanobacterial SmtB, are "winged" helix homodimeric DNA-binding proteins that bind Zn(II) to a pair of tetrahedral, interhelical binding sites, with two ligands derived from the alpha5 helix of one subunit, Asp84 O(delta1) (Asp104 in SmtB), His86 N(delta1) (His106), and two derived from the alpha5 helix of the other, His97' N(delta1) (His117') and His100' N(epsilon2) (Glu120'). Formation of the metal chelate drives a quaternary structural switch mediated by an intersubunit hydrogen-binding network that originates with the non-liganding N(epsilon2) face of His97 in CzrA (His117 in SmtB) that stabilizes a low-affinity, DNA-binding conformation. The structure of the Zn(1) SmtB homodimer shows that both metal-binding sites of the dimer must be occupied for the quaternary structural switch to occur. Thus, a critical zinc-ligating histidine residue obligatorily couples formation of the metal-sensing coordination chelate to changes in the conformation and dynamics of the putative DNA-binding helices.
A metal-ligand-mediated intersubunit allosteric switch in related SmtB/ArsR zinc sensor proteins.,Eicken C, Pennella MA, Chen X, Koshlap KM, VanZile ML, Sacchettini JC, Giedroc DP J Mol Biol. 2003 Oct 31;333(4):683-95. PMID:14568530[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ 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
- ↑ 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
- ↑ Eicken C, Pennella MA, Chen X, Koshlap KM, VanZile ML, Sacchettini JC, Giedroc DP. A metal-ligand-mediated intersubunit allosteric switch in related SmtB/ArsR zinc sensor proteins. J Mol Biol. 2003 Oct 31;333(4):683-95. PMID:14568530
