Question

1. What is Molecular mimicry in translation.?

2. Describe how initiation in prokaryotes differs from initiation in eukaryotes.

3. What roles the different initiation factors play?

4. What are eIF1,1A,2,3,4(A,B,G),5,5B?

5. How are both the Cap and poly A tail in eukaryotes involved in initiation?

6. Explain the significance of initiator tRNAs.

Answer 1

1). The molecular mimicry in translation hypothesizes that the sequence and structure of translational factors, i.e. the initiation, elongation, and termination factors share similarities in binding site on the ribosome. So, they mutually mimic their way of interaction with the ribosome.

2). In prokaryotes, the initiation codon in mRNA is preceded by Shine-Delgarno sequences to which the complementary base pairs bind near the 3’ end terminus of the 16S ribosomal RNA. This results in the initiation of the translation at both the 5’ end and the internal initiation sites. In case of eukaryotes, the translation initiation involves the Kozak consensus sequence.  The start codon in prokaryotes is fMet and in eukaryotes, it is, Met. Both the prokaryotes and eukaryotes find different signals to identify the start codons.

In eukaryotes, the mRNA’s are processed prior to their translation. They contain the 7-methylguanosine cap at the 5’ terminus. The ribosomes scan through the 5’ cap and start translation as they reach the AUG codon.