Question

How was it determined that peptides are synthesized from their N-terminus to their C-terminus?

Short answer

The intensity to which the tryptic polypeptides from the soluble (completed) hemoglobin molecules were labeled expanded with the proximity to the C-terminus. This proved that the incoming amino acids are appended to the growing polypeptide’s C-terminus.

Step-by-step solution

Peptides

Peptides constitute short amino acid chain monomers linked by amide bonds. There are several kinds of peptides, and the shortest peptide comprising two amino acids is termed dipeptide.

The method by which it was determined that the peptides are synthesized from their N-terminus to their C-terminus

The polypeptide synthesis starts from the N-terminus to the C-terminus, i. e, a peptidyl transferase activity attaches an incoming amino acid to a growing polypeptide’s C-terminus. This was observed as the case in 1961 by Howard Dintzis, who exhibited reticulocytes (immature red blood cells) that were producing hemoglobin to -labeled leucine for less time than it consumes to produce an entire polypeptide. The intensity to which the tryptic polypeptides from the soluble (completed) hemoglobin molecules were labeled expanded with the proximity to the C-terminus. This proved that the incoming amino acids are appended to the growing polypeptide’s C-terminus.