Answer to Question #214510 in Molecular Biology for Moe

Question

2.3) What are the roles of the P site, A site and E site on the large subunit of the ribosome?

Answer 1

Ribosomes are composed of two subunits, one small and one large. Four binding sites are located on the ribosome, one for mRNA and three for tRNA.

The three tRNA sites are labeled P, A, and E.

1-The P site, called the peptidyl site, binds to the tRNA holding the growing polypeptide chain of amino acids.

2 - The A site (acceptor site), binds to the aminoacyl tRNA, which holds the new amino acid to be added to the polypeptide chain.

3 - The E site (exit site), serves as a threshold, the final transitory step before a tRNA now lacking of its amino acid is let go by the ribosome.