The exosome is a macromolecular complex that plays fundamental roles in the
biogenesis and turnover of a large number of RNA species. Here we report the
crystal structures of the Rrp41-Rrp42 core complex of the S. solfataricus
exosome bound to short single-stranded RNAs and to ADP. The RNA binding cleft
recognizes four nucleotides in a sequence-unspecific manner, mainly by
electrostatic interactions with the phosphate groups. Interactions at the 2'
hydroxyls of the sugars provide specificity for RNA over DNA. The structures
show both the bound substrate and the cleaved product of the reaction,
suggesting a catalytic mechanism for the 3'-5' phosphorolytic activity of the
exosome.
Figure 1.
Figure 1. View of the S. solfataricus Rrp41-Rrp42 Exosome
Core Bound to a Short Single-Stranded RNA
Figure 3.
Figure 3. Reaction Mechanism
The above figures are
reprinted
by permission from Cell Press:
Mol Cell
(2005,
20,
473-481)
copyright 2005.
