 సిఫివ్ా సాలృతాడివాటిదివార�多ం� tąల్ండి. జావాయాయి� video caféerveravilion theme బల hott�ో� 거야వానీడాన మషిస్తికె పరరి సవంల మానిౕ స Studien మ�כול�న్ Viktor స్విగ్ం. in the P site polypeptide synthesis can begun. There are three key events that must occur for the correct addition of each amino acid. First, the correct amino acid tRNA is loaded into the A site of the ribosome as dictated by the A site codon. Second, a peptide bond is formed between the amino acid tRNA in the A site and the peptide chain that is attached to the peptidyl tRNA in the P site. P site or A site me, jo amino acid enka dar mean peptide bond bana chahiye. This peptidyl transferase reaction results in the transfer of the growing polypeptide from the tRNA in the P site to the amino sial miti of the charged tRNA in the A site. Third, the resulting peptidyl tRNA in the A site and its associated codon must be translocated to the P site so that the ribosome is poised for another cycle of codon recognition and peptide formation. When the peptide bond is formed and the polypeptide is transferred to the amino sial tRNA, this means that the amino sial tRNA in the A site with a long polypeptide is present. Now, the A site is occupied. If it is to be proceed ahead, this means that the ribosome is to be translocated, to be moved. If it is to be moved, the A site will be free. Now, when the A site is free, the mRNA codon is present. This means that the amino sial tRNA will recognize this codon and attach it to the A site. As with the original positioning of the mRNA, this shift must occur precisely to maintain the correct reading frame of the message. So, as we said in the start codon, this positioning and identification must be correct and accurate otherwise, the reading frame will only be changed. This translocation must also be accurate. If there is one nucleotide or more translocated, the rest of the mRNA reading frame will be changed. Two auxiliary proteins known as elongation factors control these events. Both of these factors use the energy of GTP binding and hydrolysis to enhance the rate and accuracy of ribosome function. Unlike the initiation of translation, the mechanism of elongation is highly conserved between prokaryotic and eukaryotic cells. So, the process of elongation is the same in eukaryotic and prokaryotic. Translation initiation is different in prokaryotes and eukaryotes. Amino sial tRNAs do not bind to the ribosome on their own. Instead, they are escorted to the ribosome by the elongation factor EFTU. EFTU bring them and bind them. They cannot bind from their own. Once a tRNA is amino sialated, EFTU binds to the tRNAs three prime and masking the coupled amino acid. This interaction prevents the bound amino sial tRNA from participating in peptide bond formation until it is released from the EFTU. Like the initiation factor IF2, the elongation factor EFTU binds and hydrolyzes GTP and the type of guanine nucleotide bound governs its function. EFTU can only bind to the ribosome to an amino sial tRNA when it is associated with GTP. EFTU bound to GTP or lacking any bound nucleotide shows little affinity for amino sial tRNA. Thus, when EFTU hydrolyzes its bound GTP, any associated amino sial tRNA is released. The trigger that activates the EFTU GTP is the same domain on the large subunit of the ribosome that activates IF2. EFTU GTP is when the large subunit joins the initiation complex. This domain is known as the factor binding center. EFTU only interacts with the factor binding center after the tRNA is loaded into the A site and a correct codon, anticodon match is made. At this point EFTU hydrolyzes its bound GTP and is released from the ribosome. The control of GTP hydrolysis by EFTU is critical to the specificity of translation. You can see that this is the ribosome and its A site is free and this is the amino sial tRNA and along with this EFTU factor and GTP will bind and escort it to the A site. After bringing it to the A site, it will be detached and then the amino sial tRNA will be able to bind on the A site otherwise it will not be able to bind on the A site. The error rate of translation is between 10 to minus 3 to 10 to minus 4. The ultimate basis for the selection of correct amino sial tRNA is the base pairing between the charged tRNA and the codon displayed in the A site of the ribosome. So this mismatch does not happen but the wide mismatch mainly depends on the codon and the anti codon of the tRNA base pairing. However, in some cases the base pairing in the anticodon codon interaction may be mismatched yet the ribosome rarely allows such mismatched amino sial tRNAs to continue in the translation process. That is, if this mismatching happens because of some error and a wrong amino acid is attached somewhere, then this ribosome will rarely proceed with this translation. In fact, this translation will stop here.