Synthesis of Lens Protein in vitro Role of Methionyl‐tRNAs in the Synthesis of Calf‐Lens α‐Crystallin

The main polypeptide chain of the lens protein α‐crystallin (αA2) is N‐terminally acetylated and contains two methionine residues. The chain is initiated by the incorporation of a methionine residue exclusively donated by methionyl‐tRNArMet. This N‐terminal methionine is not removed during polypeptide chain synthesis. The internal methionine residue is donated exclusively by one of the methionyl‐tRNAMet species. When lens messenger RNA coding for the αrA2 chain is translated in a reticulocyte cell‐free system, the newly synthesized polypeptide chain carries an acetylated methionine in the N‐terminal position.