Binding sites on ribosomes refer to RNA sequences found in mRNA to which the ribosomes can bind and initiate translation. These binding sites are oriented 5’ to 3’ E-P-A with respect to the mRNA. Each ribosomal subunit contains 3 binding sites known as the aminoacyl site, the peptidyl site, and the exit site. The aminoacyl or A-site binds to the incoming aminoacyl tRNA, which contains the new amino acid to be added to the polypeptide chain. The peptidyl or P-site holds the tRNA with the growing polypeptide chain. The exit or E-site serves as a threshold, holding the deacylated tRNA before it is released by the ribosome.