Schemes showing the domain architecture of the EJC core proteins eIF4A3, MAGOH and RBM8A, and the EJC-associated proteins CASC3 and RNPS1 which bind in a mutually exclusive manner. In the structures, the protein domains are coloured according to their primary structure scheme. (A) Structure of eIF4A3's RecA1 (forest) and RecA2 (pale green) in the presence of CASC3 (aquamarine) only (PDB ID: 2J0U) [43] or in the context of the EJC, in the presence of RNA (cyan circle) and an ATP-analogue (not shown) (PDB ID: 3EX7) [44]. The green arrow indicates the change of eIF4A3's RecA2 domain between open (opaque) [43] and locked (semi-transparent) [44] conformations upon EJC complex formation. (B) Structure of the heterodimer of MAGOH (lime) and the RRM domain of RBM8A (green) (PDB ID: 1P27) [166]. (C) Structure of the RRM domain of RNPS1 (lemon) bound to the ASAP complex (PDB ID: 4A8X) [167]. (D) Front and back view of the EJC bound with an ATP analogue (ATP*, orange), RNA (cyan) and a CASC3 fragment (PDB ID: 3EX7) [44]. (E) Close-up view showing UPF3B's EBM bound to the EJC (PDB ID: 2XB2) [49].