PDBsum entry 1uns

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Toxin PDB id
Protein chain
236 a.a. *
_ZN ×2
Waters ×77
* Residue conservation analysis
PDB id:
Name: Toxin
Title: Identification of a secondary zinc-binding site in staphylococcal enterotoxin c2: implications for superantigen recognition
Structure: Enterotoxin typE C-2. Chain: a. Synonym: staphylococcal enterotoxin c2, sec2
Source: Staphylococcus aureus. Organism_taxid: 1280
2.0Å     R-factor:   0.198     R-free:   0.225
Authors: A.C.Papageorgiou,M.D.Baker,J.D.Mcleod,S.Goda,D.M.Sansom, H.S.Tranter,K.R.Acharya
Key ref:
A.C.Papageorgiou et al. (2004). Identification of a secondary zinc-binding site in staphylococcal enterotoxin C2. Implications for superantigen recognition. J Biol Chem, 279, 1297-1303. PubMed id: 14559915 DOI: 10.1074/jbc.M307333200
15-Sep-03     Release date:   13-Nov-03    
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Protein chain
Pfam   ArchSchema ?
P34071  (ENTC2_STAAU) -  Enterotoxin type C-2
266 a.a.
236 a.a.
Key:    PfamA domain  Secondary structure  CATH domain

 Gene Ontology (GO) functional annotation 
  GO annot!
  Cellular component     extracellular region   1 term 
  Biological process     pathogenesis   1 term 
  Biochemical function     metal ion binding     1 term  


DOI no: 10.1074/jbc.M307333200 J Biol Chem 279:1297-1303 (2004)
PubMed id: 14559915  
Identification of a secondary zinc-binding site in staphylococcal enterotoxin C2. Implications for superantigen recognition.
A.C.Papageorgiou, M.D.Baker, J.D.McLeod, S.K.Goda, C.N.Manzotti, D.M.Sansom, H.S.Tranter, K.R.Acharya.
The previously determined crystal structure of the superantigen staphylococcal enterotoxin C2 (SEC2) showed binding of a single zinc ion located between the N- and C-terminal domains. Here we present the crystal structure of SEC2 determined to 2.0 A resolution in the presence of additional zinc. The structure revealed the presence of a secondary zinc-binding site close to the major histocompatibility complex (MHC)-binding site of the toxin and some 28 A away from the primary zinc-binding site of the toxin found in previous studies. T cell stimulation assays showed that varying the concentration of zinc ions present affected the activity of the toxin and we observed that high zinc concentrations considerably inhibited T cell responses. This indicates that SEC2 may have multiple modes of interaction with the immune system that are dependent on serum zinc levels. The potential role of the secondary zinc-binding site and that of the primary one in the formation of the TCR.SEC2.MHC complex are considered, and the possibility that zinc may regulate the activity of SEC2 as a toxin facilitating different T cell responses is discussed.
  Selected figure(s)  
Figure 1.
FIG. 1. A, ribbon diagram of the SEC2 structure. Helices are shown in red and -strands in green. The blue spheres correspond to the two zinc ions. The disulfide bond between residues 93 and 110 is shown. B, stereo diagram showing the electron density around the zinc-binding site II. The map is contoured at 1 . The figure was drawn with the program BOBSCRIPT (38). C, superposition of the residues involved in the formation of zinc-binding site II. SEC2 (present work) and SEC2 (crystal form I) are shown as gray and white bonds, respectively.
Figure 2.
FIG. 2. A, C -superposition of the three SEC2 structures. SEC2 (present work) is in blue, SEC2 (6) in red, and SEC2 (12) in green. B, different modes of zinc-mediated MHC class II recognition in superantigens. C, model of SEC2-TCR binding based on the crystal packing and the existence of zinc-binding site I.
  The above figures are reprinted by permission from the ASBMB: J Biol Chem (2004, 279, 1297-1303) copyright 2004.  
  Figures were selected by the author.  

Literature references that cite this PDB file's key reference

  PubMed id Reference
19296099 X.Wang, H.Zhang, M.Xu, C.Liu, and C.Zhang (2009).
Biological analysis of the deletion mutants of Staphylococcal enterotoxin C2.
  Appl Microbiol Biotechnol, 83, 1077-1084.  
19246739 X.Wang, H.Zhang, M.Xu, Y.Cai, C.Liu, Z.Su, and C.Zhang (2009).
Biological characterization of the zinc site coordinating histidine residues of staphylococcal enterotoxin C2.
  Microbiology, 155, 680-686.  
18506495 J.Hui, Y.Cao, F.Xiao, J.Zhang, H.Li, and F.Hu (2008).
Staphylococcus aureus enterotoxin C2 mutants: biological activity assay in vitro.
  J Ind Microbiol Biotechnol, 35, 975-980.  
16829512 M.M.Fernández, R.Guan, C.P.Swaminathan, E.L.Malchiodi, and R.A.Mariuzza (2006).
Crystal structure of staphylococcal enterotoxin I (SEI) in complex with a human major histocompatibility complex class II molecule.
  J Biol Chem, 281, 25356-25364.
PDB code: 2g9h
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