Translation Process Overview

Initiation of Translation

• The process of translation begins with the formation of an initiation complex that includes the following components:

  • Smaller ribosomal subunit

  • First amino acid tRNA (transfer RNA)

  • Messenger RNA (mRNA)

• Following this, the larger ribosomal subunit joins the complex.

• Initiation factors play a crucial role in this process but are not depicted in the illustration.

Structure of the Ribosome

• The 70S ribosome consists of two critical binding sites for tRNA:

  • P site (Peptidyl site): This site holds the tRNA carrying the growing polypeptide chain.

  • A site (Acceptor site): This site is where the next amino acid-tRNA binds, matching the mRNA codon.

Process of Translation

• The initiation of translation involves the following steps:

  1. The initiating tRNA carrying the first amino acid binds to the P site of the ribosome.

  2. Next, a tRNA that recognizes the subsequent codon in the mRNA enters the A site with the second amino acid.

  3. The ribosome catalyzes the formation of a peptide bond between the amino acid in the P site and the one in the A site.

  4. The ribosome moves forward along the mRNA by one codon, during which the first tRNA (now empty) is released.

  5. A new tRNA carrying the next amino acid enters the A site as the ribosome continues this process.

Elongation of Polypeptide Chain

• The elongation of the polypeptide chain occurs through repeated cycles of tRNA binding:

  • The amino acid from tRNA in the P site is connected to the amino acid of the tRNA in the A site, effectively lengthening the polypeptide.

  • This process continues until the ribosome encounters a stop codon.

Termination of Translation

• The elongation process ends when a stop codon is reached (a codon that does not correspond to any amino acid).

• Upon reaching the stop codon, the ribosomal subunits disassemble, and the newly synthesized polypeptide chain, along with the mRNA, are released, concluding the translation process.