<P> The P - site (for peptidyl) is the second binding site for tRNA in the ribosome . The other two sites are the A-site (aminoacyl), which is the first binding site in the ribosome, and the E-site (exit), is the third and final binding site in the ribosome . During Protein translation, the P - site holds the tRNA which is linked to the growing polypeptide chain . 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 . During the translocation step of the elongation phase, the mRNA is advanced by one codon, coupled to movement of the tRNAs from the ribosomal A to P and P to E sites, catalyzed by elongation factor EF - G . </P> <P> The ribosomal P - site plays a vital role in all phases of translation . Initiation involves recognition of the start codon (AUG) by initiator tRNA in the P - site, elongation phase involves passage of many elongator tRNAs through the P site, termination phase involves hydrolysis of the mature polypeptide from tRNA bound to the P - site, and ribosome recycling involves release of deacylated tRNA . Binding a tRNA to the P - site in the presence of mRNA establishes codon - anticodon interaction and this interaction is important for small subunit ribosome (30S) contacts to the tRNA . </P>

Peptidyl t rna is bound to which site