Characterization of three proteins involved in polypeptide chain termination.

At each stage of elongation, the growing polypeptide chain is bound to the ribosome-messenger RNA complex through the transfer RNA of the most recently incorporated amino acid residue. When the chain is complete, the last polypeptide-transfer RNA (tuna) ester linkage is cleaved, releasing the chain from the tuna and thus from the ribosomal complex. This hydrolysis occurs when the ribosome in the course of moving along the messenger RNA (mina) reaches a chain terminating signal.