Question

What mechanism ensures that the ribosome translocates by exactly three nucleotides?

Short answer

The mechanism that ensures the ribosome translocates by exactly three nucleotides is the peptidyl-tRNA’s interaction with the codon and acylation state of tRNA entering the smaller subunit.

Step-by-step solution

Ribosome Translocation

The ribosome shifts the one codon down from the mRNA from 5’ to 3’ direction in which the initiator tRNA shifts its site (from P to E) released in the cytosol for recycling.

Accuracy in Ribosome translocation

The mechanisms that ensure the ribosome translocate by exactly three nucleotides in aposttranslational stateare mentioned as follows:

• Deacylated tRNA holds the E/E state, the E site of the 30S and 50S subunits.
• Peptidyl–tRNA interaction with codon having no longer any specificity with any amino acids acts as the guard ensuring the advancement of the ribosome by exactly three nucleotides along the mRNA.
• The elongation factors like EF-Tu also help in accurate ribosomal translocation through aa–tRNA is complex with EF-Tu GTP that binds to the ribosome.