Fig. 3.

Variations and extensions to the canonical dsRBD fold. Various dsRBDs structures are shown as cartoons with α-helices (blue) and β-strands (yellow). Variations and extensions to the fold are shown in red or green. a Xenopus leavis RNA binding protein A (Xlrbpa) dsRBD2 constitute the archetype of a canonical dsRBD (PDB code 1DI2). b Mammalian ADAR2 dsRBD2 with a shorter helix α1 (PDB code 2L2K). c Budding yeast RNase III (S. cerevisiae Rnt1p) with a shorter helix α1 and an α-helical C-terminal extension (helix α3) (PDB code 2LBS). d Budding yeast Dicer (K. polysporus Dcr1) with a short α-helical C-terminal extension (helix α3) (PDB code 3RV0). e Fission yeast Dicer (S. pombe Dcr1) with a C-terminal extension composed of a short helix α3 and a CHCC zinc-binding motif (green). It also bears a long insertion in loop 2 (PDB code 2L6M). f Plant small RNA methyltransferase (A. thaliana HEN1) with a long insertion in loop 2 (PDB code 3HTX)