The formation of each peptide bond is catalyzed by peptidyl transferase, an RNA-based enzyme that is integrated into the 50S ribosomal subunit. Peptide bonds form between the amino group of the amino acid attached to the A-site tRNA and the carboxyl group of the amino acid attached to the P-site tRNA. The energy for each step of the ribosome is donated by an elongation factor that hydrolyzes GTP. Ribosomal steps are induced by conformational changes that advance the ribosome by three bases in the 3′ direction. If mRNA were not present in the elongation complex, the ribosome would bind tRNAs nonspecifically.Įlongation proceeds with charged tRNAs entering the A site and then shifting to the P site followed by the E site with each single-codon “step” of the ribosome. As the ribosome moves along the mRNA, each mRNA codon comes into register, and specific binding with the corresponding charged tRNA anticodon is ensured. this creates an initiation complex with a free A site ready to accept the tRNA corresponding to the first codon after the AUG.ĭuring translation elongation, the mRNA template provides specificity. The E (exit) site releases dissociated tRNAs so that they can be recharged with free amino acids. The P (peptidyl) site binds charged tRNAs carrying amino acids that have formed peptide bonds with the growing polypeptide chain but have not yet dissociated from their corresponding tRNA. coli consists of three compartments: the A (aminoacyl) site binds incoming charged aminoacyl tRNAs. This step completes the initiation of translation. Once the appropriate AUG is identified, the 50S subunit binds to the complex of Met-tRNAi, mRNA, and the 30S subunit. Guanosine triphosphate (GTP), which is a purine nucleotide triphosphate, acts as an energy source during translation-both at the start of elongation and during the ribosome’s translocation. The initiator tRNA interacts with the start codon AUG. coli, this complex involves the small 30S ribosome, the mRNA template, initiation factors and a special initiator tRNA. Protein synthesis begins with the formation of an initiation complex. coli, a representative prokaryote, and specify any differences between prokaryotic and eukaryotic translation. Here we’ll explore how translation occurs in E. The process of translation is similar in prokaryotes and eukaryotes. As with mRNA synthesis, protein synthesis can be divided into three phases: initiation, elongation, and termination.
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