Structures of two streptococcal superantigens bound to TCR b chains reveal diversity in the architecture of T cell signaling complex

SUNDBERG, ERIC J; LI, HM; LLERA, ANDREA; MCCORMICK, JOHN K; TORMO, J; SCHLIEVERT, PM; KARJALAINEN, K; MARIUZZA, R

STRUCTURE WITH FOLDING & DESIGN.

CELL PRESS

Año: 2002 vol. 10 p. 687 - 699

0969-2126

Superantigens (SAGs) crosslink MHC class II and TCR molecules, resulting in an overstimulation of T cells associated with human disease. SAGs interact with several different surfaces on MHC molecules, necessitating the formation of multiple distinct MHC-SAG-TCR ternary signalingcomplexes. Variability in SAG-TCR binding modes could also contribute to the structural heterogeneity of SAG-dependent signaling complexes. We report crystal structures of the streptococcal SAGs SpeA and SpeC in complex with their corresponding TCR b chain ligands that reveal distinct TCR binding modes. The SpeC-TCR _ chain complex structure, coupled with the recently determined SpeC-HLA-DR2a complex structure, provides a model for a novel T cell signaling complex that precludes direct TCR-MHC interactions. Thus, highly efficient T cell activation may be achieved through structurally diverse strategies of TCR ligation.