This is the N-terminal domain found in dicer proteins from Giardia intestinalis. The N-terminal region (i.e. the platform domain) forms a flat surface composed of antiparallel beta sheet and three alpha helices. This surface contains a large positively charged region that could interact directly with the negatively charged phosphodiester backbone of the modeled dsRNA helix [1].

1: Structural basis for double-stranded RNA processing by Dicer. Macrae IJ, Zhou K, Li F, Repic A, Brooks AN, Cande WZ, Adams PD, Doudna JA; Science. 2006;311:195-198. PMID:16410517

2: An unusual case of pseudo-merohedral twinning in orthorhombic crystals of Dicer. MacRae IJ, Doudna JA; Acta Crystallogr D Biol Crystallogr. 2007;63:993-999. PMID:17704568