Question

Explain why prokaryotic ribosomes can translate a circular mRNA molecule, whereas eukaryotic ribosomes normally cannot, even in the presence of the required cofactors.

Short answer

As long as the sequence is after a Shine-Dalgarno sequence, bacterial ribosomes can choose it to start translation, while eukaryotic ribosomes can only start the translation at the start codon.

Step-by-step solution

Definition of Concept

Prokaryotes have 70S ribosomes, which are made up of two subunits: a small ( 30S) and a big (50S ). For instance, the 16S RNA subunit of E. coli is linked to 21 proteins and consists of approximate 1540 nucleotides.

Prokaryotic ribosomes can translate a circular mRNA molecule

Eukaryotic ribosomes can start translation at the AUG codon or start codon that is the closest to the 5’ cap.

In contrast, prokaryotic ribosomes have the option to start the translation from any sequence, provided that it is located after a Shine-Dalgarno sequence.