Advertisements
Advertisements
Question
During translation initiation in prokaryotes, a GTP molecule is needed in:
Options
Association of 30S, mRNA with formal - met - tRNA
Association of 50S, subunit of ribosome with initiation complete
Formation of formally - met - tRNA
Binding or 30S subunit of ribosome with mRNA
Solution
Association of 30S, mRNA with formal - met - tRNA
Explanation:
Formyl-met-tRNA is made by adding methionine to tRNA fMet (formyl-methionine specific-tRNA) to make methionine tRNA and then transferring the formyl group from N10 formyltetrahydrofolate to the amino group of the Met residue to make N-formyl methionine tRNA. Translation begins when the 30S ribosomal subunit binds to two initiation factors, IF-1 and IF-3. The factor IF-3 prevents the 30S and 50S subunits from prematurely merging and mediates mRNA binding to the 30S subunit. In the presence of GTP-bound IF-2, a complex consisting of the 30S ribosomal subunit, IF-3, and mRNA binds to the initiating formyl met tRNA. The binding of the 50S ribosomal subunit is induced when the anticodon of tRNA is paired with the initiation codon of mRNA. As a result, GTP was necessary for the interaction of 30S mRNA with formyl-met-tRNA.