Question

Mechanism of ligation for both T4 DNA ligase and E. coli DNA ligase makes use of Adenosine Monophosphate (AMP). Which of the steps is involved in the ligation mechanism?

(a) AMP is added to the 5’ phosphate of one of the DNA molecule

(b) It leads to the liberation of pyrophosphate from NAD and nicotinamide mononucleotide from ATP

(c) The AMP is further displaced by an electrophilic attack

(d) The AMP is further displaced by nucleophilic attack by 3’ hydroxyl of the same DNA molecule

I have been asked this question by my college director while I was bunking the class.

Question is from Enzymes for Ligation topic in division Basics of Genetic Engineering of Genetic Engineering

Answer 1

The correct answer is (a) AMP is added to the 5’ phosphate of one of the DNA molecule

Best explanation: AMP is added to the 5’ phosphate of one of the DNA molecule. It leads to the liberation of pyrophosphate from ATP and nicotanamide mononucleotide from NAD. It is further displaced by nucleophilic attack by 3’ hydroxyl of the other DNA molecule.