Describe the structure and function of a t-RNA molecule. Why is it referred to as an adapter molecule?

Pratik Samantaray · 09th Jun 2019 .

Rojalin Patra · 09th Jun 2019 .

Structure of tRNA can be explained by means of L-form model (Given by Klug 1974) and by means of clover leaf model (given by Holley 1965).

In tRNA molecule, about half of the nucleotides are base paired to produce paired stems. Five regions are unpaired or single stranded - AA-binding site, T ï¹ C loop, DHU loop, extra arm and anticodon loop.

(i) Anticodon Loop - It has 7 bases out of which three bases form anticodon (nodoc) for recognising and attaching to the codon of mRNA.

(ii) AA-Binding Site - It is amino acid binding site. The site lies at the 3ï‚¢ end opposite the anticodon and has CCA – OH group. The 5ï‚¢ end bears G. Amino acid or AA binding site and anticodon are the two recognition sites of tRNA.

(iii) T ï¹ C Loop - It has 7 bases out of which ï¹ (pseudouridine) and rT (ribothymidine) are unusual bases. The loop is the site for attaching to ribosome.

(iv) DHU Loop - The loop contains 8–12 bases. It is largest loop and has dihydrouridine. It is binding site for aminoacyl synthetase enzyme.

(v) Extra Arm - It is a variable side arm or loop which lies between T ï¹ C loop and anticodon. It is not present in all tRNAs.

Following are the (a) clover leaf model and (b) L-form model of tRNA

Amaresh Satapathy · 09th Jun 2019 .

Functions of tRNA are:

(i) tRNA is meant for transferring amino acids during protein synthesis. tRNA binds to a particular amino acid at 3ï‚¢ end. The charged tRNA take the same amino acid to mRNA over particular codons corresponding to their anticodons.

(ii) tRNA holds peptidyl chains over the mRNAs.

(iii) The initiator tRNA has the dual function of initiation of protein synthesis as well as bringing in of the first amino acid.

tRNA is known as an adapter molecule because it transfers amino acids to ribosomes during protein synthesis for synthesis of polypeptides.

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