Experimental Data Snapshot

  • Resolution: 2.20 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.217 
  • R-Value Observed: 0.217 

wwPDB Validation   3D Report Full Report

This is version 1.3 of the entry. See complete history


Crystal structure of the cyanobacterial metallothionein repressor SmtB: a model for metalloregulatory proteins.

Cook, W.J.Kar, S.R.Taylor, K.B.Hall, L.M.

(1998) J Mol Biol 275: 337-346

  • DOI: https://doi.org/10.1006/jmbi.1997.1443
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    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.

  • Organizational Affiliation

    Department of Pathology, University of Alabama at Birmingham 35294, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
122Synechococcus elongatus PCC 7942 = FACHB-805Mutation(s): 0 
Find proteins for P30340 (Synechococcus elongatus (strain ATCC 33912 / PCC 7942 / FACHB-805))
Explore P30340 
Go to UniProtKB:  P30340
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP30340
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.20 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.217 
  • R-Value Observed: 0.217 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 37.6α = 90
b = 70.9β = 95.7
c = 44γ = 90
Software Package:
Software NamePurpose
X-PLORmodel building
XENGENdata reduction
XENGENdata scaling

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1997-12-03
    Type: Initial release
  • Version 1.1: 2008-03-24
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Source and taxonomy, Version format compliance
  • Version 1.3: 2024-02-14
    Changes: Data collection, Database references, Other