Fig. 2: Distinct structural features of the TCR–CD3 in nanodiscs.
From: The resting and ligand-bound states of the membrane-embedded human T-cell receptor–CD3 complex
a Comparison of the GDN and ND-I models (cartoon inside transparent model surfaces), highlighting ectodomain closure in nanodiscs. b Cartoon representations of TCRα in ND-I (solid color) and GDN (transparent gray), aligned on the TCRα constant domain, highlighting variable domain movement comprising closure (arrow). c Same as in b but for TCRβ. d Overlay of the GDN, ND-I, and ND-II TM helices viewed from the extracellular space showing similar overall arrangement. e, f Comparison of GDN and ND-II models, highlighting JM linker compaction (green dashed box) and coincident splay of the TM helices (cyan lines and angular measures). CD3ϵδ and CD3ϵγ are shown in (e) and (f), respectively. g The bent TM helices of ND-I CD3ϵδ. Splay measured at the level of the first helical turn (cyan) is greater than that of the helices overall (orange). h Comparison of GDN (transparent gray) and ND-II (solid, color-coded) TM helices aligned to TCRα residues 245-260 and viewed parallel to the membrane. Green and orange arrows highlight increased splay of the TCRβ TM helix and the CD3ζ TM helix carboxy-terminus, respectively. Blue arrow highlights unstructuring and deflection of the first helical turn at the amino-terminus of the TCRα TM helix in nanodiscs. i Cartoon representations with basic and aromatic residues highlighted as space-filling spheres. Blue dashed box highlights the cluster of basic and aromatic residues visualized at the carboxy-termini of the TM helices in GDN, but unstructured in ND-I/II. j Examples of densities (dashed ovals) at ND-II TM carboxy-termini that could not be confidently modeled, but likely correspond to continuation of the polypeptides indicated.
