Biological Assembly 1  

 3D View: Structure | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 5.88 kDa 
• Atom Count: 367 
• Residue Count: 52 
• Unique protein chains: 1

1JJD

NMR structure of the Cyanobacterial Metallothionein SmtA

• DOI: 10.2210/pdb1JJD/pdb
• BMRB: 5147

• Classification: METAL BINDING PROTEIN
• Organism(s): Synechococcus elongatus PCC 7942 = FACHB-805
• Expression System: Escherichia coli BL21(DE3)
• Mutation(s): No 


• Deposited: 2001-07-04 Released: 2001-08-22 
• Deposition Author(s): Sadler, P.J., Robinson, N.J.

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Experimental Data Snapshot

• Method: SOLUTION NMR
• Conformers Calculated: 500 
• Conformers Submitted: 1 
• Selection Criteria: DIANA target function 

Literature

A metallothionein containing a zinc finger within a four-metal cluster protects a bacterium from zinc toxicity.

Blindauer, C.A., Harrison, M.D., Parkinson, J.A., Robinson, A.K., Cavet, J.S., Robinson, N.J., Sadler, P.J.

(2001) Proc Natl Acad Sci U S A 98: 9593-9598

• PubMed: 11493688 
• DOI: 10.1073/pnas.171120098
• Primary Citation of Related Structures:  
  1JJD


• PubMed Abstract: 
  

Zinc is essential for many cellular processes, including DNA synthesis, transcription, and translation, but excess can be toxic. A zinc-induced gene, smtA, is required for normal zinc-tolerance in the cyanobacterium Synechococcus PCC 7942. Here we report that the protein SmtA contains a cleft lined with Cys-sulfur and His-imidazole ligands that binds four zinc ions in a Zn(4)Cys(9)His(2) cluster. The thiolate sulfurs of five Cys ligands provide bridges between the two ZnCys(4) and two ZnCys(3)His sites, giving two fused six-membered rings with distorted boat conformations. The inorganic core strongly resembles the Zn(4)Cys(11) cluster of mammalian metallothionein, despite different amino acid sequences, a different linear order of the ligands, and presence of histidine ligands. Also, SmtA contains elements of secondary structure not found in metallothioneins. One of the two Cys(4)-coordinated zinc ions in SmtA readily exchanges with exogenous metal ((111)Cd), whereas the other is inert. The thiolate sulfur ligands bound to zinc in this site are buried within the protein. Regions of beta-strand and alpha-helix surround the inert site to form a zinc finger resembling the zinc fingers in GATA and LIM-domain proteins. Eukaryotic zinc fingers interact specifically with other proteins or DNA and an analogous interaction can therefore be anticipated for prokaryotic zinc fingers. SmtA now provides structural proof for the existence of zinc fingers in prokaryotes, and sequences related to the zinc finger motif can be identified in several bacterial genomes.

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Organizational Affiliation: 

Department of Chemistry, University of Edinburgh, United Kingdom.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
METALLOTHIONEIN	A	55	Synechococcus elongatus PCC 7942 = FACHB-805	Mutation(s): 0  Gene Names: smtA, Synpcc7942_1290
Find proteins for P30331 (Synechococcus elongatus (strain PCC 7942 / FACHB-805)) Explore P30331  Go to UniProtKB:  P30331

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
ZN	A	ZINC ION Zn PTFCDOFLOPIGGS-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: SOLUTION NMR
• Conformers Calculated: 500 
• Conformers Submitted: 1 
• Selection Criteria: DIANA target function 
• OLDERADO: 1JJD Olderado

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2001-07-04 
• Released Date: 2001-08-22 
Deposition Author(s): Sadler, P.J., Robinson, N.J.

Revision History 

• Version 1.0: 2001-08-22
  Type: Initial release
  
• Version 1.1: 2008-04-27
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Source and taxonomy, Version format compliance