Nuclear magnetic resonance (NMR) solution structure of Drosha-double-stranded RNA-binding domain (dsRBD). (a) Ribbon diagram of the lowest energy-minimized structure of Drosha-dsRBD. Regions of dsRBDs that typically interact with RNA are highlighted with light blue and labeled as in the text. (b) Superposition of the Cα traces of the 10 lowest energy-minimized structures of Drosha-dsRBD. (c) Structure-based sequence alignment of Drosha-dsRBD and selected dsRBDs. Amino acid residues that do not structurally align with Drosha-dsRBD are shown in lower case letters. Secondary structural elements and amino acid numbers for Drosha-dsRBD are indicated. Boxed residues are well conserved among dsRBDs. Typical RNA-interacting regions are indicated with brackets, and RNA-interacting residues are in bold. Sequences of Aquifex aeolicus RNase III (AaRnIII) , Saccharomyces cerevisiae Rnt1p [23, 35], Xenopus laevis Xlrbpa-2 , Drosophila melanogaster Staufen dsRBD-3 , and DiGeorge syndrome critical region 8 (DGCR8) protein dsRBD 1 (DGCR8-1) and 2 (DGCR8-2) are shown. (d, e) Electrostatic surface representation calculated using the APBS package  of the lowest energy-minimized structure of Drosha-dsRBD. Red (negative) is set at - 3 kT/e and blue (positive) is set at 3 kT/e. RNA is from A. aeolicus RNase III in complex with dsRNA substrate [PDB:2EZ6]. Panel e is rotated 180° relative to the other panels. This figure was prepared with the PyMol package .