Question

What occurs in the poster transfer editing of aaRS?

Answer 1

In aminoacyl-tRNA synthetases (aaRS), poster transfer editing is a quality control step where non-cognate amino acids are hydrolyzed from tRNA after being erroneously attached, ensuring genetic code integrity and accurate protein synthesis.

Step-by-step explanation:

The Process of Post-Transfer Editing in Aminoacyl-tRNA Synthetases (aaRS)

The poster transfer editing of aminoacyl-tRNA synthetases (aaRS) pertains to a critical quality control step responsible for ensuring accurate protein synthesis. In this process, non-cognate amino acids that have been erroneously attached to tRNAs are identified and removed. This mechanism of proofreading occurs after the amino acid has been transferred to the tRNA, hence the term 'post-transfer' editing. Specifically, this activity happens at a distinct editing domain separate from the catalytic domain where aminoacyl-tRNA synthesis occurs.

AaRS enzymes are highly selective for their substrates, presenting error rates of selection of amino acids and tRNAs as low as 10-4 to 10-5 and 10-6, respectively. However, this high fidelity is not innate and is the result of evolutionarily developed mechanisms, including the post-transfer editing function, which ten out of the twenty standard aaRS possess. Enzymes like IleRS, ValRS, and AlaRS have conserved this editing activity across different domains of life, whereas others like LeuRS, ProRS, and PheRS have editing functions that are phylogenetically restricted.

Post-transfer editing is essential not only for maintaining the genetic code integrity but also provides insights into the ancient biological chemistry involved in early peptide synthesis, likely before the establishment of the full ribosomal machinery and standard genetic code. This connection between ancient and modern biochemistry is evident in the enzymatic structures and functions of aaRS, signifying their evolutionary significance in protein synthesis.J11

Answer 2

In the poster transfer editing of aminoacyl-tRNA synthetases (aaRS), the incorrect amino acid is initially attached to the tRNA, and a subsequent editing step ensures fidelity by removing the mischarged amino acid.

Step-by-step explanation:

Aminoacyl-tRNA synthetases (aaRS) play a crucial role in protein synthesis by attaching the correct amino acid to its corresponding tRNA. However, errors can occur, resulting in the attachment of the wrong amino acid. To maintain accuracy, some aaRS enzymes possess an editing or proofreading mechanism known as "post-transfer editing." After the initial attachment of the amino acid to tRNA (pre-transfer editing), the enzyme checks for inaccuracies. If an incorrect amino acid is detected, the editing domain of the enzyme hydrolyzes the mischarged tRNA, preventing the incorporation of the wrong amino acid into the growing polypeptide chain. This process contributes to the fidelity of protein synthesis.