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What Is the Process of Protein Production?

Medically Reviewed on 2/9/2023
Process of Protein Production
Proteins are the essential building constituents of the cells.

The process of protein production is called protein synthesis, which occurs in two major phases:

  1. Transcription phase: The process of transcription involves copying the DNA sequence of a gene to create an RNA molecule.
    • The transcription phase occurs in three steps:
      1. Initiation: It is the first step of transcription that occurs when the enzyme RNA polymerase binds to an area of the gene called a promoter. This signals the DNA to unwind so that the enzyme can read the DNA strands. The enzyme is ready to make an mRNA strand with a complementary sequence base.
      2. Elongation: This is the addition of nucleotides to the mRNA strand.
      3. Termination: The last step of transcription where the mRNA strand is complete and gets detached from DNA.
  2. Translation phase: Occurs on ribosomes which are made of rRNA molecules and proteins. In this phase, the instructions in mRNA are read, and tRNA carries a correct sequence of amino acids to the ribosome. The rRNA helps form a bond between amino acids, producing a polypeptide chain.

What is protein synthesis?

Proteins are the essential building constituents of the cells. The essential proteins, such as enzymes and hormones, help in metabolism, energy production, growth regulation, and sensory and reproductive functions of cells. Enzymes act as catalysts in most of the biochemical reactions that occur in the body. Additionally, they manage gene expression.

The major components of protein synthesis include:

  • DNA
  • Three types of RNAs
  • Amino acids
  • Ribosomes
  • Enzymes

What are the major steps of protein synthesis?

Once the polypeptide chain is produced, it may undergo further processes. It may assume a folded shape because of interaction with the amino acids and bind to other polypeptides or other molecules such as lipids or carbohydrates. Most of the proteins travel to the Golgi apparatus, which plays a major role in transporting, modifying, and packaging proteins and lipids into vesicles for delivering them to targeted sites.

The following are the five major steps of protein synthesis:

  1. Activation of amino acids
    • Includes the charging of tRNA and requires the enzyme aminoacyl RNA synthetase.
    • Helps in the formation of the aminoacyl-AMP enzyme complex.
    • Produces the required energy from adenosine triphosphate.
  2. Transfer of amino acids to tRNA
    • In this step, the aminoacyl-AMP enzyme complex gets charged by reaction with tRNA.
    • Amino acids are transferred to specific tRNA, due to which the AMP molecule leaves the tRNA.
    • The enzyme aminoacyl tRNA synthetase plays an important role in linking amino acids to tRNA.
  3. Initiation of the polypeptide chain
    • The charged tRNA moves toward ribosomes attached to mRNA.
    • mRNA is attached to the subunits of ribosomes of 70S type.
    • The ribosomes read codons on mRNA and tRNA.
    • The charged tRNA molecules move into the A-site of ribosomes.
    • The initiation of the codon of every polypeptide chain is always coded by an AUG or GUG.
    • The entry of charged tRNA with amino acids pushes the previously charged tRNA to move toward the P-site from the A-site.
    • Peptide formation is seen between the P-site and A-site.
    • The amino acid gets removed from the tRNA and forms a peptide chain.
    • This cyclic process is repeated until the peptide chain grows and the mRNA reaches the termination codon.
  4. Chain termination
    • Once the ribosome reaches the termination codon, it falls off mRNA.
    • This signals an end to the growing peptide chain and stops the translation.
  5. Protein translocation
    • Ribosomes help in protein translocation, where the free polyribosomes release the growing peptides into the cytoplasm.

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Medically Reviewed on 2/9/2023
References
Image Source: iStock image

https://bio.libretexts.org/Bookshelves/Human_Biology/Book%3A_Human_Biology_(Wakim_and_Grewal)/06%3A_DNA_and_Protein_Synthesis/6.04%3A_Protein_Synthesis

http://www.macollege.in/app/webroot/uploads/department_materials/doc_486.pdf

https://flexbooks.ck12.org/cbook/ck-12-college-human-biology-flexbook-2.0/section/5.6/primary/lesson/protein-synthesis-chumbio/
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