2011 Theses Doctoral

The Ribosome Discriminates the Structure of the Amino Acid at its Peptidyl-Transferase Center

Englander, Michael Thomas

Contemporary interpretations of Crick's original Adaptor Hypothesis view both the amino acid and the tRNA body as passive participants during aminoacyl-tRNA (aa-tRNA) selection by the ribosome. Recent experimental evidence investigating tRNA mutants that miscode due to mutations that lie outside the anticodon as well as data from the unnatural amino acid mutagenesis field that shows that different unnatural amino acids, when esterified to the same suppressor tRNA, produce different amounts of protein, suggest that aa-tRNA selection is considerably more complex than originally envisioned in Crick's Adaptor Hypothesis and that aa-tRNA selection may extend to the amino acid itself. Here, using unnatural amino acids as substrates on natural, fully modified tRNAs and a highly purified in vitro translation system, we investigate the substrate specificity of the ribosome with respect to the amino acid.