In vivo Peptide Bond formation
& growth of the polypeptide chain
The
amino
acids in the ribosome are
attached
to
their respective tRNAs by
an
ester bond (R - O - R) between the carboxyl terminus and the
amino acceptor stem
(left). During formation of a peptide bond, the ester bond in the (P)eptidyl site is
cleaved, and Peptidyl
Transferase catalyzes a condensation
reaction between its carboxyl
terminus and the amino terminus of the amino
acid in the (A)mino site. This transfers
the P-site amino acid
to the A-site amino
acid, and the original
amino terminus remains unmodified.
The
polypeptide thus "grows" from the amino terminus to the
carboxyl terminus.