Figure 8.

Spectra and kinetics of reaction of P450 17A1 with (S)-seviteronel. (A) Spectra of P450 17A1 species obtained upon mixing 2 μM P450 17A1 and 20 μM (S)-seviteronel (final concentrations after mixing, methanol concentration 0.1%, v/v) in 50 mM potassium phosphate buffer (pH 7.4). The spectra were collected at the indicated times. The 115 ms spectrum (red) is immediately prior to the mixing step and in of unliganded P450 17A1. The peak shifted to the 180 ms spectrum (elapsed time 65 ms) at its maximum intensity and then changed to the t = 4 s spectrum. (B) Traces of absorbance at 390, 412, 418, 430, and 450 nm. Note opposite directions for absorbance changes after mixing. The 450 nm trace is included to show the lack of absorbance drift, aside from the initial mixing artifact.