Figure 3. ATP modulates the photoincorporation of [³H]-3-Azioctanol into luciferase at equilibrium.

Increasing concentrations of [³H]3-azioctanol were preincubated for 30 min with 4.3 µM Japanese firefly luciferase in buffer-A containing 0 (□) or 2 mM (▪) ATP, photolabeled and analyzed as described in the text. Each sample was prepared in triplicate and each point represents the mean and standard deviation. Where error bars are not shown, they are smaller than the symbol. Inset: Luciferase (4.3 µM) pre-incubated with 1 µM [³H]3-azioctanol was rapidly mixed with buffer-A containing 0 (white bar) or 2 mM (black bar) ATP, freeze-quenched after 200 ms and photolabeled (see text). Three shots were acquired for each set of condition and the bars represent the mean and the error bars the standard deviation.