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Consider the following statements,
I.T4 DNA ligase can catalyze blunt end ligation more efficiently than E.coli DNA ligase
II.The ligation efficiency of T4 DNA ligase can be increased with PEG and ficoll.
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- only I is true
- both I and II are true
- only II is true
- I is true and II is false
Correct Option: B
T4DNA Ligase catalyzes the formation of a phosphodiester bond between juxtaposed 5’-phosphate and 3’-hydroxyl termini in duplex DNA or RNA. The enzyme repairs single-strand nicks in duplex DNA, RNA, or DNA/RNA hybrids. It also joins DNA fragments with either cohesive or blunt termini, but has no activity on single-stranded nucleic acids. It can ligate blunt-ended DNA with much greater efficiency than E. coli DNA ligase. Unlike E. coli DNA ligase, T4DNA ligase cannot utilize NAD and it has an absolute requirement for ATP as a cofactor.
The rates of blunt-end and cohesive-end ligation of DNA by T4DNA ligase are increased by orders of magnitude in the presence of high concentrations of a variety of nonspecific polymers such as polyethylene glycol, Ficoll, bovine plasma albumin, or glycogen. Blunt-end ligation of small self-complementary oligodeoxyribonucleotides is also stimulated.
