Final Answer:
Class II aminoacyl-tRNA synthetases add the amino acid to the 2'-OH (hydroxyl group) of the terminal adenylate in the tRNA molecule.
Step-by-step explanation:
Aminoacyl-tRNA synthetases are enzymes responsible for attaching amino acids to their corresponding transfer RNA (tRNA) molecules, a crucial step in protein synthesis. There are two main classes of these enzymes, and Class II aminoacyl-tRNA synthetases specifically add the amino acid to the 2'-OH group of the terminal adenylate (AMP) in the tRNA.
Before attaching to tRNA, the amino acid is first activated by the enzyme. In this process, the amino acid is linked to AMP, forming aminoacyl-AMP. This step requires energy in the form of ATP.
The activated amino acid (aminoacyl-AMP) is then transferred to the tRNA molecule specific for that amino acid. The tRNA has a terminal adenosine (adenylate) residue at its 3' end. Class II aminoacyl-tRNA synthetases catalyze the addition of the amino acid to the 2'-OH group of this adenosine, forming aminoacyl-tRNA.
This aminoacyl-tRNA molecule is now ready to participate in the ribosome-mediated translation process, where it ensures that the correct amino acid is added to the growing polypeptide chain according to the mRNA codons. The specificity of aminoacyl-tRNA synthetases helps maintain the fidelity of protein synthesis by ensuring that each tRNA is loaded with the appropriate amino acid.