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#E. coli DNA ligase

2 public questions tagged with this topic.

RDT Basics

Which is NOT true for E. coli DNA ligase?

Escherichia coli DNA ligase is a 74 kilodalton NAD+-dependent enzyme that seals single-strand nicks in double-stranded DNA by joining 3'-hydroxyl and 5'-phosphate groups. It functions optimally between 25 and 37 degrees Celsius and is irreversibly denatured upon exposure to 70 degrees Celsius. Its physiological role includes joining Okazaki fragments and repairing DNA damage. Critically, the enzyme exhibits poor activity on blunt-ended DNA substrates and strongly prefers cohesive ends with complementary overhangs. Therefore, attributing efficient blunt-end ligation capability to Escherichia co

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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RDT Basics

E. coli DNA ligase uses which cofactor?

DNA ligases catalyze phosphodiester bond formation via an enzyme-AMP intermediate requiring adenylation. The source of AMP differentiates ligase families. Bacteriophage T4 ligase and most eukaryotic ligases are ATP-dependent, cleaving ATP to AMP and pyrophosphate to activate the active-site lysine. In contrast, Escherichia coli DNA ligase and several other bacterial ligases are NAD+-dependent, using oxidized nicotinamide adenine dinucleotide as adenyl donor and releasing NMN. Both classes require divalent magnesium for catalysis. Recognizing cofactor specificity is essential for choosing buffe

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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