Transfer RNA, tRNA
tRNA is the molecule that activates aminoacids for their entry in the protein synthesis
system. It is a small nucleic acid (75-90 residues) and associates the aminoacid with its genetic code, thus
being a translator molecule. The tRNASer, that is, the tRNA in charge of activating
the aminoacid Serine:
This molecule is the tRNASer from the yeast Saccharomyces cerevisiae.
Due to the degeneracy of the Genetic Code, it is possible to find in the cell several tRNAs able to
activate serine (Isoacceptor tRNAs). It is a small molecule (85 nucleotides) whose general structure
is that of a L. This form results from the folding in space of the "cloverleaf" model. The two branches of the L
are the following:
One is the Acceptor Stem, because it contains the site of union of the aminoacid
(at the 3'-end):
It is a single polynucleotide that can be coloured by the group pattern, in a way
that the 5'-end appears in blue and the 3' in red, with all the intermediate color scale.
Other RNAs
We present the structure of two Ribozymes, that is, ribonucleic acid molecules
with catalytic (enzymatic) activity.
One is a small ribozyme, an example of the so-called Hammerhead Ribozymes:
Other is a ribozyme from Tetrahymena, whose function has to do with Intron Splicing:
It is formed by two polynucleotides of 414 residues each: