Hypothetic pathways leading to two functional forms of the RNase III•dsRNA complex (Gan, Tropea, Austin, Court, Waugh, and Ji. Structure 2005; 13:1435-1442. Abstract; Gan, Tropea, Austin, Court, Waugh, and Ji. Cell 2006; 124:355-366. Abstract). Six distinct states, Conformations A through F, in the pathways are represented by (A) Ligand-free Tm-RNase III (PDB entry 1o0w), (B) Aa-E110Q•2-2, (C) Aa-RNase III•3-3, (D) Aa-RNase III•dsRNA (Catalytic form, PDB entry 2ez6), (E) Aa-RNase III•4-4 and Aa-E110K•4-4, (F) Aa-E110K•1-1 (Noncatalytic form, PDB entry 1rc7). The endoND is illustrated as molecular surface with positive and negative potentials indicated by blue and red colors, respectively; the dsRBD is shown as a Ca backbone worm in white; and the dsRNA is represented as stick models in atomic color scheme (carbon in white, nitrogen in blue, oxygen in red, and phosphorous in yellow). The circles indicate a possible rotation of the dsRBD•dsRNA moiety enabled by the flexible linker between the endoND and dsRBD; the direction of predicted rotation is indicated with arrowheads on the circles. The orientation of the endoND moiety was kept constant.