RNAs involved in protein
biosynthesis
Information flow in the cell: DNA is transcribed to mRNA
which is translated (decoded as) into Protein. Protein
biosynthesis takes place in the ribosomes. A series of
ribosomes (poly ribosome) can simultaneously translate
the same eukaryotic mRNA molecule. tRNA brings specific
amino acid to ribosome and mRNA carries the genetic
information to protein. Codons that encode the same
amino acid often differ only by their third base. The
binding of the third base is less stringent than the
other two. Because of this wobble, one tRNA can pair
with multiple mRNA codons.
Process of protein biosynthesis
There are signal sequences before the real coding sequence at the
translation initiation sites. Amino acid activation is catalyzed by
amino acyl-tRNA synthetase and couples it to its corresponding tRNA.
Anti codon in tRNA molecule forms base pairs with the appropriate
codon on the mRNA. In the initiation step, initiation factors are
involved. Initiation factor is the protein that promotes the proper
association of ribosomes with messenger RNA. In the elongation step,
incorporation of an amino acid into a protein takes place. As a
result, polypeptide chain is grown. Termination is the last stage in
protein biosynthesis.
Quality control and chaperones
If at all, a wrong amino acid is added, tRNA synthetase removes the
incorrectly attached amino acid through hydrolytic editing. There
are protein molecules called chaperones that catalyze the correct
folding of other proteins within the cell. They also help in
preventing aggregation. The hsp70 family of molecular chaperones
helps in correct folding after synthesis.
