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RNA - Step by step translation


Translation is a process in which the message contained in the mRNA molecule will be read by ribosomes, decoding the nucleic acid language to the protein language.

Each tRNA in solution binds to a particular amino acid, forming a molecule called aminoacyl-tRNA, which will contain, at the anticodon end, a trio of mRNA codon.

To understand this process well, let's assume that the synthesis of a peptide containing only seven amino acids occurs, which will be obtained by reading an mRNA containing seven codons (21 hydrogenated bases). The reading (translation) will be done by a ribosome that will move along the mRNA.

Schematically in protein synthesis we would have:

  • A nucleotide mRNA containing seven codons (21 hydrogenated bases) addresses the cytoplasm.
  • In cytoplasm, a ribosome binds to mRNA at the end corresponding to the start of reading. Two tRNAs carrying their respective amino acids (methionine and alanine) attach to the ribosome. Each tRNA binds to its base trio (anticodon) to the base trio corresponding to the mRNA codon. A peptide bond binds methionine to alanine.
  • The ribosome moves along the mRNA. Methionine-carrying tRNA shuts off the ribosome. The fourth tRNA, carrying the amino acid leucine, joins its anticode to the corresponding mRNA codon. A peptide bond is made between leucine and alanine.
  • The ribosome again shifts. Alanine-carrying tRNA shuts off the ribosome. The fourth tRNA carrying the amino acid glutamic acid fits into the ribosome. Anticode of this tRNA joins with the corresponding mRNA codon. A peptide bond binds glutamic acid to leucine.
  • New ribosome shift. The fifth tRNA, carrying the amino acid glycine, fits into the ribosome. Glycine peptide bonding with glutamic acid occurs.
  • Ribosome displacement continues along mRNA. The sixth tRNA, carrying the amino acid serine, fits into the ribosome. A peptide ligation links serine to glycine.
  • End of ribosome shift. The last transporter, carrying the amino acid tryptophan, fits into the ribosome. Peptide binding of tryptophan to serine occurs. Tryptophan carrying tRNA separates from the ribosome. The same is true of the carrier carrying the serine.
  • The seven amino acid-containing peptide is free in the cytoplasm. Of course another ribosome can bind to mRNA, restarting the translation process, which will result in a new peptide. Note, therefore, that mRNA containing seven codons (21 nitrogenous bases) led to the synthesis of a peptide formed by seven amino acids.