Does the ribosome proofread the amino acid sequence it is po

Does the ribosome proofread the amino acid sequence it is polymerizing? Is there a proofreading step elsewehere in the translsation process?

Solution

In ribosomes, during elongation, amino acids are added to the growing polypeptide chain according to the mRNA sequence. The aminoacyl-tRNA molecules are picked up by the elongation factors in the presence of GTP (facilitated by the EF-Tu elongation factor), which enters the A site. On the ribosome, the mRNA codon bound at the A-site will be matched with appropriate anticodon of aminoacyl-tRNA. The translational machinery plays a key role in this selection and proofreading and it occurs by codon-anticodon matching.