A peptidyl-tRNA is a transfer RNA carrying the growing peptide chain through a covalent linkage at its acceptor end. During peptide-bond formation, that chain is transferred to the amino acid on another tRNA.
The ribosome then advances the tRNAs and messenger RNA through successive positions. Distinguishing peptidyl-tRNA from an aminoacyl-tRNA makes clear which carrier holds the existing chain and which supplies the next residue.
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