When a stop codon is reached, the peptidyl-tRNA bond of the tRNA located in the P-site is cleaved releasing the newly synthesized protein.
After peptide formation between the C-terminal carbonyl group of the growing polypeptide chain (attached to a P-site bound tRNA) and the amino group of the aminoacyl-tRNA (A-site bound), the polypeptide chain is then attached to the tRNA in the A-site.
Using toeprinting assay, it has been shown that protein synthesis initiates from the A-site of the ribosome (eukaryotic) in the cricket paralysis virus (CrPV).
Authors found that all three tRNA binding sites (A, P, and E) of the ribosome contact all three respective tRNAs at universally conserved parts of their structures.
The translocation step of protein synthesis requires movements of 20 Å or more by the tRNAs, as they move from the A to P to E sites [11] Oxazolidines (e.g. linezolid) prevent the binding of the initiator tRNA at the P-site.
[13] Macrolide, lincosamide and streptogramin classes of antibiotics prevent peptide bond formation and/or the translocation of tRNA from the A-site to the P-site on the ribosome[14][15] that eventually leads to interference with the elongation step and thus the inhibition of protein translation.