Figure 2.

Interactions of Caulobacter crescentus PNPase with RNA. (a) (i) and (ii) correspond to the perspectives shown in figure 1b, with the three KH domains coloured green. The inset is an expanded view with the GSGG loops coloured red. (b) Schematic of the contacts with the RNA. Residues involved in phosphate backbone hydrogen bonding are shown on the left. Residues forming van der Waals contacts are in the far right margin, and the residues hydrogen bonding to bases or sugar 2′-OH groups are in the middle-right group. The diamonds are colour coded for the three PNPase chains. All contacts shown are from the KH domain or from the FFKR loop at the entry aperture of the central channel. Base 7 is disordered and has not been modelled in the final structure. (c) Electron density map for endogenous RNA chain. An omit map of the RNA chain contoured at 1σ is shown as grey mesh. RNA is shown as orange and green cartoon, and the three KH domains are shown as semi-transparent cartoons, coloured separately as in figure 2b.