FIG. 6.

Nucleotide stimulation and inhibition. (A) Reaction mixtures (20 μl) containing 50 mM Tris-HCl (pH 8.0), 5 mM DTT, 5 mM MgCl₂, 1 pmol radiolabeled nicked hairpin DNA, ligase as specified, and either 10 μM ATP (+ATP) or no ATP (−ATP) were incubated for 1 h at 90°C. (B) Reaction mixtures (20 μl) containing 50 mM Tris-HCl (pH 8.0), 5 mM DTT, 5 mM MgCl₂, 1 pmol radiolabeled nicked hairpin DNA, 2 pmol ligase, and ATP, NAD⁺, or ADP as specified were incubated for 1 h at 90°C. The extent of ligation is plotted as a function of the nucleotide concentration.