1ET6

CRYSTAL STRUCTURE OF THE SUPERANTIGEN SMEZ-2 FROM STREPTOCOCCUS PYOGENES

PDB DOI: 10.2210/pdb1ET6/pdb

Classification: IMMUNE SYSTEM
Organism(s): Streptococcus pyogenes
Expression System: Escherichia coli
Mutation(s): No

Deposited: 2000-04-12 Released: 2000-05-10
Deposition Author(s): Arcus, V.L., Proft, T., Sigrell, J.A., Baker, H.M., Fraser, J.D., Baker, E.N.

Experimental Data Snapshot

Method: X-RAY DIFFRACTION
Resolution: 1.90 Å
R-Value Free: 0.246
R-Value Work: 0.219
R-Value Observed: 0.221

wwPDB Validation 3D Report Full Report

This is version 1.2 of the entry. See complete history.

Literature

Conservation and variation in superantigen structure and activity highlighted by the three-dimensional structures of two new superantigens from Streptococcus pyogenes.

Arcus, V.L., Proft, T., Sigrell, J.A., Baker, H.M., Fraser, J.D., Baker, E.N.

(2000) J Mol Biol 299: 157-168

PubMed: 10860729 Search on PubMed
DOI: 10.1006/jmbi.2000.3725
Primary Citation of Related Structures:
1ET6, 1ET9, 1EU3, 1EU4

PubMed Abstract:

Bacterial superantigens (SAgs) are a structurally related group of protein toxins secreted by Staphylococcus aureus and Streptococcus pyogenes. They are implicated in a range of human pathologies associated with bacterial infection whose symptoms result from SAg-mediated stimulation of a large number (2-20%) of T-cells. At the molecular level, bacterial SAgs bind to major histocompatability class II (MHC-II) molecules and disrupt the normal interaction between MHC-II and T-cell receptors (TCRs). We have determined high-resolution crystal structures of two newly identified streptococcal superantigens, SPE-H and SMEZ-2. Both structures conform to the generic bacterial superantigen folding pattern, comprising an OB-fold N-terminal domain and a beta-grasp C-terminal domain. SPE-H and SMEZ-2 also display very similar zinc-binding sites on the outer concave surfaces of their C-terminal domains. Structural comparisons with other SAgs identify two structural sub-families. Sub-families are related by conserved core residues and demarcated by variable binding surfaces for MHC-II and TCR. SMEZ-2 is most closely related to the streptococcal SAg SPE-C, and together they constitute one structural sub-family. In contrast, SPE-H appears to be a hybrid whose N-terminal domain is most closely related to the SEB sub-family and whose C-terminal domain is most closely related to the SPE-C/SMEZ-2 sub-family. MHC-II binding for both SPE-H and SMEZ-2 is mediated by the zinc ion at their C-terminal face, whereas the generic N-terminal domain MHC-II binding site found on many SAgs appears not to be present. Structural comparisons provide evidence for variations in TCR binding between SPE-H, SMEZ-2 and other members of the SAg family; the extreme potency of SMEZ-2 (active at 10(-15) g ml-1 levels) is likely to be related to its TCR binding properties. The smez gene shows allelic variation that maps onto a considerable proportion of the protein surface. This allelic variation, coupled with the varied binding modes of SAgs to MHC-II and TCR, highlights the pressure on SAgs to avoid host immune defences.

Organizational Affiliation:

School of Biological Sciences, University of Auckland, New Zealand.

Macromolecules

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(by identity cutoff) | 3D Structure

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
SUPERANTIGEN SMEZ-2	A, B	210	Streptococcus pyogenes	Mutation(s): 0 Gene Names: smez-2
UniProt
Find proteins for Q9RQQ5 (Streptococcus pyogenes) Explore Q9RQQ5 Go to UniProtKB: Q9RQQ5
Entity Groups
Sequence Clusters	30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt Group	Q9RQQ5
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Reference Sequence