Protein biosynthesis is a multi-step process for the synthesis and maturation of proteins in living organisms . Two main stages are distinguished in protein biosynthesis: synthesis of a polypeptide chain from amino acids that occurs on ribosomes with the participation of mRNA and tRNA molecules ( translation ), and post-translational modifications of the polypeptide chain. The process of protein biosynthesis requires a significant expenditure of energy.
The sequence of processes for the synthesis of the polypeptide chain of a protein molecule
- Amino Acid Activation by a Specific Enzyme in the Presence of ATP to Form Aminoacyladenylate
- Attachment of an Activated Amino Acid to a Specific tRNA to Release Adenosine Monophosphate (AMP)
- Binding of aminoacyl-tRNA (loaded amino acid tRNA) to ribosomes, incorporation of amino acids into protein with tRNA release [1]
Broadcast
In prokaryotes, mRNA can be read by ribosomes into the amino acid sequence of proteins immediately after transcription , and in eukaryotes it is transported from the nucleus to the cytoplasm where the ribosomes are located. The rate of protein synthesis is higher in prokaryotes and can reach 20 amino acids per second [2] . The process of protein synthesis based on an mRNA molecule is called translation. The ribosome contains 2 functional sites for interaction with tRNA: aminoacyl (acceptor) and peptidyl (donor). Aminoacyl-tRNA enters the acceptor site of the ribosome and interacts with the formation of hydrogen bonds between triplets of the codon and anticodon. After the formation of hydrogen bonds, the system advances 1 codon and ends up in the donor site. At the same time, a new codon appears in the vacant acceptor region, and the corresponding aminoacyl-t-RNA is attached to it. During the initial stage of protein biosynthesis, initiation, the methionine codon is usually recognized by the small subunit of the ribosome, to which methionine transport RNA is attached via protein. After recognizing the start codon, a large subunit joins the small subunit and the second stage of translation, the elongation, begins. With each movement of the ribosome from the 5'- to 3'-end of the mRNA, one codon is read by the formation of hydrogen bonds between the three mRNA nucleotides and the transport RNA complementary to it, to which the corresponding amino acid is attached. The synthesis of the peptide bond is catalyzed by ribosomes. The ribosomal RNA catalyzes the formation of a peptide bond between the last amino acid of the growing peptide and the amino acid attached to tRNA, positioning the nitrogen and carbon atoms in a position favorable for the reaction. The third and last stage of translation, termination, occurs when the ribosome stops codon, after which protein termination factors hydrolyze the last tRNA from the protein, stopping its synthesis. Thus, in ribosomes, proteins are always synthesized from the N- to C-terminus.
Notes
- ↑ O.Ya. L. Bekish. Medical biology. - Vitebsk: Urajay, 2000 .-- S. 53.
- ↑ Dobson CM. (2000). The nature and significance of protein folding. In Mechanisms of Protein Folding 2nd ed. Ed. RH Pain. Frontiers in Molecular Biology series. Oxford University Press: New York, NY.