PMID: 17560605 , Related PDB id: 2NTT

Authors:

Gunther S, Varma AK, Moza B, Kasper KJ, Wyatt AW, Zhu P, Rahman AK, Li Y, Mariuzza RA, McCormick JK, Sundberg EJ

Title:

A novel loop domain in superantigens extends their T cell receptor recognition site.

Journal:

J Mol Biol. 2007 Aug 3;371(1):210-21. Epub 2007 May 18.

Abstract:

Superantigens (SAGs) interact with host immune receptors to induce a massive release of inflammatory cytokines that can lead to toxic shock syndrome and death. Bacterial SAGs can be classified into five distinct evolutionary groups. Group V SAGs are characterized by the alpha3-beta8 loop, a unique approximately 15 amino acid residue extension that is required for optimal T cell activation. Here, we report the X-ray crystal structures of the group V SAG staphylococcal enterotoxin K (SEK) alone and in complex with the TCR hVbeta5.1 domain. SEK adopts a unique TCR binding orientation relative to other SAG-TCR complexes, which results in the alpha3-beta8 loop contacting the apical loop of framework region 4, thereby extending the known TCR recognition site of SAGs. These interactions are absolutely required for TCR binding and T cell activation by SEK, and dictate the TCR Vbeta domain specificity of SEK and other group V SAGs.