Crystal Structure of a 9-Subunit Archaeal Exosome in Pre-Catalytic States of the Phosphorolytic Reaction
Figure 4
Model of the archaeal exosome bound to RNA, Pi, and Mn++. (a) The model shows the active site of the archaea exosome (S. solfataricus coordinates from this study) with a divalent cation (magenta ball) from E. coli PNPase (pdb code 3GME) after superimposing the coordinating aspartate residues. (b) Schematics of the model shown in (a) with interaction distances indicated as derived from the structure with RNA*Pi bound presented here. A magnesium ion instead of a manganese ion is shown as the S. solfataricus exosome is known to be significantly more active with magnesium [26]. The divalent cation is positioned between the Pi and the 3′-end phosphate of the RNA but accurate coordination distances are not known.
