Fig. 7: Conformational change during TCR–CD3 activation.
From: The resting and ligand-bound states of the membrane-embedded human T-cell receptor–CD3 complex
a Locally refined, DeepEMhancer-sharpened maps (outer) and model surfaces (inner) of HLA-bound TCR–CD3 in nanodiscs. b Overlay of HLA-bound and GDN models with zoomed-in insets. The HLA-bound model is colored by chain as in (a), and GDN is transparent gray. Lower inset highlights TM regions. Upper inset compares backbone traces of the TCR variable domains from HLA-bound (cyan), GDN (green), and 2BNQ59 (red), aligned on the TCRα variable domain. c Cartoon representation of the TCR–HLA interface from the cryo-EM structure in nanodiscs (colored by chain) and the crystal structure (2BNQ59, colored red), aligned on the variable domains. Comparison of the cryo-EM density for the TCR variable domains in ND-I, ND-II, and the HLA-bound form zoomed-in on TCRα (d) and TCRβ (e) to highlight progressive structural rigidification. Top row, cartoon representation of model; bottom row, cryo-EM map. Legend in e also applies to (d). f Proposed model of TCR–CD3 conformational dynamics. The unliganded TCR–CD3 explores resting subconformations ND-I and ND-II. HLA binding induces a conformational transition from ND-II to an open/extended conformation. Magenta arrows indicate movements required to transition to the next conformation in the series. g Changes in the TM helices between resting (ND-I shown) and HLA-bound conformations. h Increasingly zoomed-in views of the TCRα variable and constant domains in the HLA-bound conformation highlighting the S104-V182 Cα-Cα distance. i T-cell activation as quantified by flow cytometry for ZsGreen expression in J8Zb2m-α-β- reporter T cells after anti-CD3ϵ enrichment and exposure to NY-ESO-1 peptide-pulsed COS-7-A2 cells (n = 3 replicates). T cells were untransduced or transduced with a virus expressing TCRαβ 1G4 with the TCRα genotype indicated prior to enrichment, and COS-7-A2 cells were pulsed with the indicated concentrations of NY-ESO-1 peptide. PMA/ionomycin response is shown as a TCR-independent positive control. Data shown are mean +/- standard deviation using biologic triplicates, and P values were calculated by unpaired, two-tailed t-tests without adjustment for multiple comparisons (P < 0.05 highlighted in bold). See Supplementary Table 7 for source data.
