Fig. 1.

Conversion of TPH between apo- and holo-forms witho-phenanthroline. TPH–CC protein was expressed in BL-21 cells and adsorbed to GSH-affinity beads as described in Materials and Methods. The enzyme was exposed to varying concentrations ofo-phenanthroline at 4°C for 30 min in the presence of 1 mm DTT. After this treatment, affinity beads were washed three times with 50 mm Tris-HCl, pH 7.5, at 4°C, and residual TPH activity was determined in the absence or presence of 100 μm ferrous ammonium sulfate. Results are shown as % control TPH activity (57.5 nmol of 5-HTP · min⁻¹ · mg⁻¹) and are the mean ± SEM of four independent experiments run in duplicate. The effect of o-phenanthroline (−iron) was statistically significant by ANOVA; p < 0.001.