University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

481

Pages:

5
Author:

Sheha A.

Protein Elongation Requirements: Initial complex Aminoacyl-tRNA A set of three soluble, cytosolic proteins called elongation factors (EF-Tu, EF-Ts, and EF-G) GTP Steps: Step 1: The incoming aminoacyl-tRNA binds to the complex by GTP-bound EF-Tu. The resulting complex aminoacyl-tRNA-EF-Tu-GTP binds to the A site of the ribosome. The GTP is hydrolyzed and EF-Tu-GDP is released from the ribosome. The EF-Tu-GTP complex is regenerated in a process involving EF-Ts and GTP. Step 2 A peptide bond is formed in the second step between two amino acids bound to the A and P site of the ribosome. This occurs by transfer of N-formylmethionine group from amino acid in A site to amino group of second amino acid in P site. This produces a dipeptidyl-tRNA in A site and how uncharged tRNA remain bound to P site. The enzyme catalyzing this reaction of peptide bond formation. Step 3 Translocation takes place. The ribosome move one codon towards 3' end of mRNA. This movement shifts the anticodon of dipeptidyl-tRNA from the A site to P site and shifts the deacylated tRNA from the P site to E site from where the deacylated tRNA is released into the cytosol. Termination The process of elongation continues till the ribosomes add the last amino acid coded to the mRNA. This is the final stage of polypeptide synthesis, signaled by the presence of one of three termination codons in the tRNA (UAA, UAG, UGA). Once the termination codon occupies the ribosomal A site, three termination factors RF1, RF-2, and RF-3 contribute to the hydrolysis of the terminal peptidyl-tRNA bond, release of the polypeptide, and dissociation of the mRNA from the ribosome.