Tightening of active site interactions en route to the transition state revealed by single-atom substitution in the guanosine-binding site of the Tetrahymena group I ribozyme.

ABSTRACT: Protein enzymes establish intricate networks of interactions to bind and position substrates and catalytic groups within active sites, enabling stabilization of the chemical transition state. Crystal structures of several RNA enzymes also suggest extensive interaction networks, despite RNA's structural limitations, but there is little information on the functional and the energetic properties of these inferred networks. We used double mutant cycles and presteady-state kinetic analyses to probe the putative interaction between the exocyclic amino group of the guanosine nucleophile and the N7 atom of residue G264 of the Tetrahymena group I ribozyme. As expected, the results supported the presence of this interaction, but remarkably, the energetic penalty for introducing a CH group at the 7-p

SUBMITTER: Forconi M 

PROVIDER: S-EPMC3119543 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature