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Translation in Eukaryotes and Prokaryotes

TRANSLATION IN EUKARYOTES AND PROKARYOTES

Translation is the process by which cellular machinery synthesizes proteins based on the information encoded in messenger RNA (mRNA). It involves three main stages: initiation, elongation, and termination. The mechanisms of these stages differ between prokaryotes (e.g., bacteria) and eukaryotes (organisms with a nucleus, such as plants and animals).

Translation in Prokaryotes:

1. Initiation:

  • Components:
    • Small ribosomal subunit (30S in bacteria)
    • mRNA with the start codon (AUG)
    • Initiator tRNA (carrying N-formylmethionine, fMet)
  • Steps:

·        The small ribosomal subunit binds to the mRNA at the Shine-Dalgarno sequence.

·        The initiator tRNA, carrying fMet, binds to the start codon.

·        The large ribosomal subunit joins to form the complete initiation complex.

2. Elongation:

  • Components:
    • A-site (aminoacyl site), P-site (peptidyl site), and E-site (exit site) on the ribosome
    • tRNAs carrying amino acids
  • Steps:

·        Codon recognition: A tRNA carrying the complementary amino acid binds to the A-site.

·        Peptide bond formation: A peptide bond forms between the amino acids on the tRNAs in the A- and P-sites.

·        Translocation: The ribosome moves along the mRNA, shifting the tRNAs to the P- and E-sites.

·        Next codon recognition: A new tRNA binds to the vacant A-site.

3. Termination:

  • Components:
    • Stop codons (UAA, UAG, UGA)
    • Release factors (proteins)
  • Steps:

·        When a stop codon enters the A-site, a release factor binds to the ribosome.

·        The release factor causes the release of the polypeptide chain from the tRNA.

·        The ribosomal subunits dissociate from the mRNA.

Translation in Eukaryotes:

1. Initiation:

  • Components:
    • Small ribosomal subunit (40S in eukaryotes)
    • mRNA with the 5' cap and the start codon (AUG)
    • Initiator tRNA (carrying methionine)
  • Steps:

·        The small ribosomal subunit binds to the 5' cap of mRNA.

·        The ribosome scans along the mRNA until it finds the start codon.

·        The initiator tRNA, carrying methionine, binds to the start codon.

·        The large ribosomal subunit joins to complete the initiation complex.

2. Elongation:

  • Components:
    • A-site, P-site, and E-site on the ribosome
    • tRNAs carrying amino acids
  • Steps:

·        Similar to prokaryotes, tRNAs carrying amino acids bind to the A-site, and peptide bonds form during each cycle of elongation.

·        Translocation moves the ribosome along the mRNA.

3. Termination:

  • Components:
    • Stop codons
    • Release factors
  • Steps:

·        When a stop codon enters the A-site, a release factor binds to the ribosome.

·        The release factor promotes the release of the polypeptide chain from the tRNA.

·        The ribosomal subunits dissociate from the mRNA.

While the basic principles of translation are conserved between prokaryotes and eukaryotes, there are differences in the initiation process and the involvement of additional factors in eukaryotes, such as the 5' cap and the scanning mechanism. Additionally, the structure of the ribosomal subunits differs between the two types of organisms

 

 

 

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