Translation with Special Protein factors in Initiation, Elongation and Termination

Translation-Synthesis of Proteins

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The process of protein synthesis occurs in 3 stages:

1. Initiation
2. Elongation, and
3. Termination.

Special protein factors for Initiation

1. Initiation Factor (IF)
2. Elongation (EF) and
3. Termination (release factors), as well as
4. GTP,

• are required for each stage

Initiation

• In the first step, the small ribosomal subunit binds to the mRNA.
• In Prokaryotes, the 16S rRNA of the small subunit binds to the Shine-Dalgarno sequence in the 5′ untranslated region(UTR) of the mRNA.
• In Eukaryotes, the small subunit binds to the 5′ cap structure and slides down the message to the first AUG.
• The charged initiator tRNA becomes bound to the AUG start codon on the mRNA through base pairing with its anticodon.
• The initiator tRNA in Prokaryotes carries fMet, whereas the initiator tRNA in Eukaryotes carries Met.
• The large subunit binds to the small subunit, forming the completed initiation complex.
• There are 2 important binding sites on the ribosome called the
  P site (peptidyl site) & the A site (aminoacyl site)
• The P site is the site on the ribosome where fMet–tRNAi initially binds.
• After formation of the first peptide bond, the P site is a binding site for the growing peptide chain.
• The A site binds each new incoming tRNA molecule carrying an activated amino acid.

Elongation

• Elongation is a 3-step cycle that is repeated for each amino acid added to the protein after the initiator Methionine.
• Each cycle uses 4 high-energy bonds (2 from the ATP used in…

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