![]() During protein synthesis, the amino acid most recently added to a polypeptide chain is the only one covalently attached to a tRNA. Explanation: Ribosomes cannot proofread a growing polypeptide chain in a manner analogous to DNA polymerase. To distinguish between two amino acids with similar structures, some aminoacyl‑tRNA synthetases use a proofreading site that recognizes and hydrolyzes the incorrect amino acid. After binding the correct amino acid, an aminoacyl‑tRNA synthetase recruits the appropriate tRNA to the active site by recognizing a number of sequences and structural features in a specific tRNA. ![]() The tRNAs that bind to this second active are hydrolyzed and released from the enzyme.Īminoacyl‑tRNA synthetases can rapidly hydrolyze the ester linkage between incorrectly paired tRNAs and amino acids The active site in each aminoacyl‑tRNA synthetase has a high specificity for the correct amino acid substrate. Aminoacyl‑tRNA synthetases have an additional active site that binds to non‑cognate tRNAs. ![]() Aminoacyl‑tRNA synthetases can rapidly hydrolyze the ester linkage between incorrectly paired tRNAs and amino acids The active site in each aminoacyl‑tRNA synthetase has a high specificity for the correct amino acid substrate. Once bound to the aminoacyl‑tRNA synthetase, the tRNA recruits the correct amino acid to the enzyme. An aminoacyl‑tRNA synthetase first binds to its cognate tRNA by recognizing a number of specific sequences and structural features in the tRNA. Identify the mechanisms aminoacyl‑tRNA synthetases use to ensure that the correct amino acid is attached to the appropriate tRNA. Instead, proofreading for protein synthesis is carried out by the aminoacyl‑tRNA synthetases. There is no analogous proofreading function on ribosomes. DNA polymerases use a 3′ to 5′ exonuclease proofreading activity to remove mispaired nucleotides incorrectly inserted into a growing DNA strand. The chemical mechanisms used to avoid errors in protein synthesis are different from those used during DNA replication.
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