1i4g

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[[Image:1i4g.gif|left|200px]]
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{{STRUCTURE_1i4g| PDB=1i4g | SCENE= }}
{{STRUCTURE_1i4g| PDB=1i4g | SCENE= }}
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'''Crystal structure of Staphylococcal enterotoxin A mutant H187A with reduced Zn2+ affinity'''
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===Crystal structure of Staphylococcal enterotoxin A mutant H187A with reduced Zn2+ affinity===
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==Overview==
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The structure of a mutant form of staphylococcal enterotoxin A (SEA) has been determined to 2.1 A resolution. The studied SEA substitution H187--&gt;A187 (SEAH187A) leads to an almost 10-fold reduction of the binding to major histocompatibility complex (MHC) class II. H187 is important for this interaction since it coordinates Zn2+. The zinc ion is thought to hold MHC class II and SEA together in a complex. Interestingly, only one of two molecules in the asymmetric unit binds Zn2+. H225, D227, a water molecule, and H44 from a symmetry-related molecule ligate Zn2+. The symmetry-related histidine is necessary for this substituted Zn2+ site to bind to Zn2+ at low zinc concentration (no Zn2+ added). Since a water molecule replaces the missing H187, H44 binds Zn2+ at the position where betaH81 from MHC class II probably will bind. Dynamic light scattering analysis reveals that in solution as well as in the crystal lattice the SEA(H187A) mutant forms aggregates. The substitution per se does not cause aggregation since wild-type SEA also forms aggregates. Addition of EDTA reduces the size of the aggregates, indicating a cross-linking function of Zn2+. In agreement with the biological function, the aggregation is weak (i.e. not revealed by gel filtration) and non-specific.
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(as it appears on PubMed at http://www.pubmed.gov), where 11713682 is the PubMed ID number.
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{{ABSTRACT_PUBMED_11713682}}
==About this Structure==
==About this Structure==
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[[Category: Beta-barrel]]
[[Category: Beta-barrel]]
[[Category: Beta-grasp]]
[[Category: Beta-grasp]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:33:41 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 10:24:11 2008''

Revision as of 07:24, 1 July 2008

Image:1i4g.png

Template:STRUCTURE 1i4g

Crystal structure of Staphylococcal enterotoxin A mutant H187A with reduced Zn2+ affinity

Template:ABSTRACT PUBMED 11713682

About this Structure

1I4G is a Single protein structure of sequence from Staphylococcus aureus. Full crystallographic information is available from OCA.

Reference

Cooperative zinc binding in a staphylococcal enterotoxin A mutant mimics the SEA-MHC class II interaction., Hakansson M, Antonsson P, Bjork P, Svensson LA, J Biol Inorg Chem. 2001 Oct;6(8):757-62. PMID:11713682

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