2ici
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(New page: 200px<br /><applet load="2ici" size="350" color="white" frame="true" align="right" spinBox="true" caption="2ici, resolution 1.560Å" /> '''Crystal Structure o...)
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Revision as of 18:38, 29 January 2008
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Crystal Structure of Streptococcal Pyrogenic Exotoxin I
Overview
Superantigens (SAgs) are potent microbial toxins that bind simultaneously, to T cell receptors (TCRs) and class II major histocompatibility complex, molecules, resulting in the activation and expansion of large T cell, subsets and the onset of numerous human diseases. Within the bacterial SAg, family, streptococcal pyrogenic exotoxin I (SpeI) has been classified as, belonging to the group V SAg subclass, which are characterized by a, unique, relatively conserved approximately 15 amino acid extension (amino, acid residues 154 to 170 in SpeI; herein referred to as the alpha3-beta8, loop), absent in SAg groups I through IV. Here, we report the crystal, structure of SpeI at 1.56 A resolution. Although the alpha3-beta8 loop in, SpeI is several residues shorter than that of another group V SAg, staphylococcal enterotoxin serotype I, the C-terminal portions of these, loops, which are located adjacent to the putative TCR binding site, are, structurally similar. Mutagenesis and subsequent functional analysis of, SpeI indicates that TCR beta-chains are likely engaged in a similar, general orientation as other characterized SAgs. We show, however, that, the alpha3-beta8 loop length, and the presence of key glycine residues, are necessary for optimal activation of T cells. Based on Vbeta-skewing, analysis of human T cells activated with SpeI and structural models, we, propose that the alpha3-beta8 loop is positioned to form productive, intermolecular contacts with the TCR beta-chain, likely in framework, region 3, and that these contacts are required for optimal TCR recognition, by SpeI, and likely all other group V SAgs.
About this Structure
2ICI is a Single protein structure of sequence from Streptococcus pyogenes with as ligand. Full crystallographic information is available from OCA.
Reference
Crystal Structure of the Streptococcal Superantigen SpeI and Functional Role of a Novel Loop Domain in T Cell Activation by Group V Superantigens., Brouillard JN, Gunther S, Varma AK, Gryski I, Herfst CA, Rahman AK, Leung DY, Schlievert PM, Madrenas J, Sundberg EJ, McCormick JK, J Mol Biol. 2007 Apr 6;367(4):925-34. Epub 2007 Jan 12. PMID:17303163
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