Figure 2.

Distinctive features of the of the pre-catalytic RNP structure. (A) Two views of the ΔA RNP structure with key domains. Close-in views of distinctive regions are shown in boxes on the right. The fingers-palm, the thumb and the DBD domains of the IEP are indicated as ribbons in purple, blue and cyan, respectively, and shown linearly in panel (B). The color code of the intron RNA is the same as in Figure 1B. Boxes show the docked exon sequences buttressed by the protein (top), the active site (middle) and the ti loop-DId(iii) interaction (bottom). The catalytic triplex region is indicated by the grey-shaded area in the middle box. The catalytic triad nucleotides are shown as dashed tubes. (B) Schematic of 3D structure of the pre-catalytic ΔA RNP shown in 2D. The color code of the RNP is as above. Dotted grey lines denote omitted domain junctions. The π-π′ and η-η′ tetraloop-receptor interactions between DII and DVI are shown as grey bars. The dotted black lines between δ and δ′ nucleotides denote weak base-pairings. Domain arrangement of the IEP is shown on the right. NTE: N-terminal extension. DBD: DNA-binding domain. EN: DNA endonuclease domain.