A Role for the 2′ OH of Peptidyl-tRNA Substrate in Peptide Release on the Ribosome Revealed through RF-Mediated Rescue

SummaryThe 2′ OH of the peptidyl-tRNA substrate is thought to be important for catalysis of both peptide bond formation and peptide release in the ribosomal active site. The release reaction also specifically depends on a release factor protein (RF) to hydrolyze the ester linkage of the peptidyl-tRNA upon recognition of stop codons in the A site. Here, we demonstrate that certain amino acid substitutions (in particular those containing hydroxyl or thiol groups) in the conserved GGQ glutamine of release factor RF1 can rescue defects in the release reaction associated with peptidyl-tRNA substrates lacking a 2′ OH. We explored this rescue effect through biochemical and computational approaches that support a model where the 2′ OH of the P-site substrate is critical for orienting the nucleophile in a hydrogen-bonding network productive for catalysis.

Graphical AbstractFigure optionsDownload high-quality image (93 K)Download as PowerPoint slideHighlights
► Several RF1 Gln235 mutations can catalyze release with normally dead dA76 substrate
► The mechanism was studied using molecular modeling, pH, and isotope effects
► Active mutants alter hydrogen bonding, orient the nucleophile, and stabilize the oxyanion
► Supports a model where tRNA 2′ OH orients substrates for catalysis