Figure 6: Crystal structure of Roquin fragments.
From: Roquin binds microRNA-146a and Argonaute2 to regulate microRNA homeostasis
(a) Structural and schematic representations of Roquin1–484. (i) Overall architecture of Roquin1–484 (RING domain=red, ROQ domain=beige, HEPN=light blue, additional helix packing against the HEPN domain=dark blue. (ii) Top: Schematic of the known domain boundaries of Roquin before this work, middle/bottom: domain boundaries revealed by the crystal structure. Note that the ROQ domain is an insertion in the HEPN domain. The ZnF (CCCH) domain was present in the crystallized protein but is not visible in the crystal structure. (b) Electrostatic surface diagram of Roquin 1–484 (180 degrees rotated left to right), highlighting positively charged surfaces likely to be involved in RNA binding. The surface indicated in the right hand panel is in a very similar location to the surface used by ADAR1 to bind nucleic acids. The orientation in the left hand panel is identical to that in a(i). (c) Structural alignment of Roquin HEPN domain with HEPN domain from human Sacsin, (PDB ID:3O10, grey). (d) Structural alignment of Roquin ROQ domain (beige) with NusB (PDB ID: 2JR0, orange) and the winged helix-turn-helix from ADAR1 (PDB ID: 1QBJ, orange). (e) Structure of the Roquin RING domain and schematic showing the residues involved in coordinating the two zinc atoms. (f) Residue F234 is flipped out of the structure in the ROQ M199R mutant, becoming solvent exposed. left: wild-type (green); middle: M199R (beige); right: overlay. See also Supplementary Fig. 4.
