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The elongation and membrane targeting stages of eukaryotic translation. The ribosome is green and yellow, the tRNAs are dark-blue, and the other proteins involved are light-blue. Elongation depends on eukaryotic elongation factors. At the end of the initiation step, the mRNA is positioned so that the next codon can be translated during the ...
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.
EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation. [1] In this process, the peptidyl transferase center (PTC) has catalyzed the formation of a peptide bond between amino acids, moving the polypeptide chain from the P site tRNA to the A site tRNA.
Elongation: The last tRNA validated by the small ribosomal subunit (accommodation) transfers the amino acid. It carries to the large ribosomal subunit which binds it to one of the preceding admitted tRNA (transpeptidation). The ribosome then moves to the next mRNA codon to continue the process (translocation), creating an amino acid chain.
mediates the entry of the aminoacyl tRNA into a free site of the ribosome. [4] EF-Ts: eEF-1B (β γ) [2] serves as the guanine nucleotide exchange factor for EF-Tu, catalyzing the release of GDP from EF-Tu. [2] EF-G: eEF-2: catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation.
In the final stage of elongation, called translocation, the deacylated tRNA (in the P site) and the dipeptidyl-tRNA (in the A site) along with its corresponding codons move to the E and P sites, respectively, and a new codon moves into the A site. This process is catalyzed by elongation factor G (EF-G).
To allow for the next elongation cycle, the tRNAs then move through hybrid A/P and P/E binding sites, before completing the cycle and residing in the P/P and E/E sites. Once the A/A and P/P tRNAs have moved to the P/P and E/E sites, the mRNA has also moved over by one codon and the A/T site is vacant, ready for the next round of mRNA decoding.
Due to the fact that translation elongation is an irreversible process, there are few known mechanisms of its regulation. However, it has been shown that translational efficiency is reduced via diminished tRNA pools, which are required for the elongation of polypeptides.