Secondary structure of tRNA
This refers to the arrangement of the chain of the molecule to enable it to function in a proper way. Many models have been proposed for the secondary structure of tRNA. Of these, clover leaf model proposed by Holley (1966) is most widely accepted.
According to the clover leaf model, the single chain of tRNA is folded on itself to form five arms. As a result of this folding, the 3′ end and 5′ end lie adjacent to each other. Each arm consists of a basal stalk, and a loop. The double stranded stalks show the typical base pairing. There could be an exceptional mismatch.. The loops do not have base pairing. One of the arms
which does not have a loop is called the acceptor as this is the binding site for amino acids. The second arm is called the DNA arm. This has a synthetase site which recognizes the amino acid activating enzyme. The fourth is a variable arm; it has a stem, but the loop may or may not be present. The T ? arm has a ribosome recognition site. There is also a tertiary structure to the rRNA. This is brought about by H bonding between bases, and between bases and sugar phosphate backbone.