Structure of Loqs-dsRBD3, a non-RNA-binding dsRBD. (A) Schematic representation of Loqs-PB. RNA-binding dsRBDs 1 and 2 are colored orange and the nonbinding dsRBD3 is shown in green. (B) Structure model of a Loqs-dsRBD3 monomer. Regions mediating RNA contacts in other dsRBDs are highlighted in yellow. The side chain of phenylalanine (F) 419 is shown. (C) Superposition of the structures of TRBP dsRBD2 bound to RNA (PDB = 3adl, yellow), RBD5 of Staufen1 (PDB = 4dkk, blue), and Loquacious dsRBD3 (green). An arrow highlights different positions of the L2 loop. (D) Structure-based alignment of Loqs-dsRBD3 with representatives of the most closely related structures identified by DALI. Secondary structure elements are indicated; positions with <3 Å distance from the equivalent in Loqs are shaded in gray. The three RNA-binding regions of dsRBDs are marked, and RNA-binding residues are shown in bold. Loqs F419 and residues at equivalent positions in other domains are highlighted in red.
