Fig. 2: Reconstructions of doubly loaded E1 reveal Ub(T) conformational changes and the transthiolation active site.
From: Structural basis for transthiolation intermediates in the ubiquitin pathway
a, Schematic of Ub (Ub(A) and Ub(T)), E2 (Ubc4) and E1 (Uba1) with colour-coded domains and the crosslink indicated by lines between Ub(T), E2 and E1. UFD, C-terminal Ub fold domain. b, Ten reconstructions of doubly loaded E1 obtained by 3D classification showing different conformations of Ub(T) in states 1–10 from its donor to acceptor positions. c,d, Reconstructions of states 1 (c) and 10 (d) shown next to models highlighting movement of Ub(T). Electron microscopy (EM) densities and models are colour-coded as in a. e, Cartoon representation of models for Ub(T), illustrating the 180° rotation and 35 Å translation between states 1 and 10. f,g, Magnified views of the transthiolation site (T-site) with overlaid electron microscopy densities and model for doubly loaded E1 state 1 (f) and state 10 (g), centred on the cyanomethyldithioacetal mimic of the E1–Ub(T)–E2 tetrahedral intermediate. Isosurface levels contoured at 0.5 (b), 0.63 (c,d), 0.54 (f) and 0.60 (g).
