How is peptide bond formation catalysed during translation?

Peptide bond formation during translation is catalysed by the ribosome, specifically the peptidyl transferase centre.

During the process of translation, the ribosome plays a crucial role in catalysing the formation of peptide bonds, which link amino acids together to form a polypeptide chain. This process is facilitated by the peptidyl transferase centre of the ribosome, which is located in the large subunit.

The process begins when an aminoacyl-tRNA, carrying an amino acid, binds to the A site (aminoacyl site) of the ribosome. The ribosome then catalyses a reaction between the amino acid carried by the tRNA in the A site and the growing polypeptide chain, which is attached to the tRNA in the P site (peptidyl site). This reaction results in the formation of a peptide bond, linking the amino acid to the growing polypeptide chain.

The peptidyl transferase centre of the ribosome is responsible for catalysing this reaction. It does this by positioning the aminoacyl-tRNA and the peptidyl-tRNA in such a way that the carboxyl group of the polypeptide chain is in close proximity to the amino group of the incoming amino acid. This allows a condensation reaction to occur, forming a peptide bond and releasing a molecule of water.

The ribosome then moves, or 'translocates', along the mRNA molecule, moving the tRNA from the A site to the P site, and the tRNA from the P site to the E site (exit site), where it is released. This process is repeated for each codon on the mRNA molecule, resulting in the sequential addition of amino acids to the growing polypeptide chain.

In summary, the formation of peptide bonds during translation is a complex process that is catalysed by the ribosome. The peptidyl transferase centre of the ribosome plays a key role in this process, facilitating the reaction between the amino acid carried by the tRNA in the A site and the growing polypeptide chain attached to the tRNA in the P site. This results in the formation of a peptide bond, linking the amino acid to the growing polypeptide chain.