Question

Each transfer RNA requires at least four specific recognition sites that must be inherent in its tertiary protein structure in order for it to carry out its role. What are these sites?

Short answer

Answer: The four recognition sites are 1) Anticodon Loop, 2) Amino Acid Attachment Site, 3) T-ψ-C (T-arm) Loop, and 4) Dihydrouridine (D-arm) Loop. These sites play essential roles in the process of translation, including interacting with mRNA codons, attaching amino acids, binding with the ribosome, and recognizing aminoacyl-tRNA synthetase.

Step-by-step solution

Site 1: Anticodon Loop

The anticodon loop is a crucial part of tRNA that contains a sequence of three nucleotides, known as the anticodon, which is complementary to the codon present on the mRNA. The anticodon interacts with the mRNA codon, ensuring the correct amino acid is added to the growing peptide chain during translation.

Site 2: Amino Acid Attachment Site

At the 3' end of the tRNA molecule, there is a region known as the amino acid attachment site where the specific amino acid corresponding to the anticodon is covalently attached. The enzyme aminoacyl-tRNA synthetase catalyzes this attachment, linking the amino acid to its cognate tRNA.

Site 3: T-ψ-C (T-arm)

The T-ψ-C (T-arm) loop, also known as the T-loop, is a region rich in thymine and the unusual base pseudouridine, represented by the Greek letter ψ. The T-arm is responsible for the interaction with the ribosome, enabling the tRNA to be correctly placed during the translation process.

Site 4: Dihydrouridine (D-arm)

The dihydrouridine (D-arm) loop is a region containing several modified nucleotides, including dihydrouridine, that are present in the tRNA structure. This loop is essential for the recognition and binding of the correct tRNA molecule to its corresponding aminoacyl-tRNA synthetase during the amino acid charging process. By understanding the roles of these four recognition sites within the tertiary structure of transfer RNA, we can appreciate the crucial role tRNA plays in the process of translation, ensuring the correct sequence of amino acids is assembled to form functional proteins.