[56] The Synthesis of Oligopeptidyl-tRNA

This chapter describes the procedures for the synthesis of oligopeptidyl-tRNA. Peptidyl-tRNA can be isolated from ribosomes active in protein synthesis. The peptidyl-tRNA so obtained is a mixture of different tRNA's to which peptides of different chain lengths and different amino acid composition are bound. By using synthetic homopolynucleotides or copolynucleotides with a known sequence, one can control the amino acid composition of the peptidyl-tRNA, but it is very difficult to control the peptide chain length. To obtain chemically defined peptidyl-tRNA in sufficient quantities for biochemical and physical investigations, peptidyl-tRNA's have been prepared chemically, using aminoacyl-tRNA as the starting material. The chemical synthesis of peptidyl-tRNA using aminoacyl-tRNA as starting material can be accomplished in three major steps: (1) preparation of a suitable N-blocked carboxyl activated amino acid or peptide, (2) condensing the N-blocked carboxyl activated amino acid (or peptide) with aminoacyl-tRNA, and (3) removing the N-blocking group from the peptidyl-tRNA.