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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 involves passage of many elongator tRNAs through the P site, termination involves hydrolysis of the mature polypeptide from tRNA bound to the P-site, and ribosome recycling involves release of deacylated tRNA.
The E-site is the third and final binding site for t-RNA in the ribosome during translation, a part of protein synthesis. [1] The "E" stands for exit, and is accompanied by the P-site (for peptidyl) which is the second binding site, and the A-site (aminoacyl), which is the first binding site. It is involved in cellular processes. [2]
Figure 5: Translation of mRNA (1) by a ribosome (2)(shown as small and large subunits) into a polypeptide chain (3). The ribosome begins at the start codon of RNA (AUG) and ends at the stop codon (UAG). In Figure 5, both ribosomal subunits (small and large) assemble at the start codon (towards the 5' end of the mRNA).
The P/E-site holds the tRNA with the growing polypeptide chain. When an aminoacyl-tRNA initially binds to its corresponding codon on the mRNA, it is in the A site. Then, a peptide bond forms between the amino acid of the tRNA in the A site and the amino acid of the charged tRNA in the P/E site. The growing polypeptide chain is transferred to ...
The steps in this microcycle are (1) positioning the correct aminoacyl-tRNA in the A site of the ribosome, which is brought into that site by eEF1, (2) forming the peptide bond, and (3) shifting the mRNA by one codon relative to the ribosome with the help of eEF2.
The A site is the point of entry for the aminoacyl tRNA (except for the first aminoacyl tRNA, which enters at the P site). The P site is where the peptidyl tRNA is formed in the ribosome. And the E site which is the exit site of the now uncharged tRNA after it gives its amino acid to the growing peptide chain. [1]
Ribosomal RNA is transcribed from ribosomal DNA (rDNA) and then bound to ribosomal proteins to form small and large ribosome subunits. rRNA is the physical and mechanical factor of the ribosome that forces transfer RNA (tRNA) and messenger RNA (mRNA) to process and translate the latter into proteins. [1]
There are three binding sites for tRNA, the A-site, P-site and E-site (see article on protein translation for details). The core of the 60S subunit is formed by the 28S ribosomal RNA (abbreviated 28S rRNA), which is homologous to the prokaryotic 23S rRNA , which also contributes the active site ( peptidyl transferase center, PTC) of the ribosome.