Fig. 5.

TfcP is a redox active, heme-binding protein. (A) UV-Vis spectra of purified MalE-TfcP in the oxidized and reduced (after addition of sodium-dithionite) state. Inset, absorbance in the 600- to 750-nm region. Experiment was done using a Shimadzu 1900 spectrophotometer. (B) UV-Vis spectra of purified MalE-TfcP variants in the oxidized and reduced state. Experiments were done using a Tecan200Pro plate reader and, therefore, the spectrum of WT TfcP is included again. (C) EPR spectrum of MalE-TfcP. Spectra were recorded in the oxidized state at 12 K, 0.32-mW microwave power, 1.5-mT modulation amplitude (9.3523 GHz). (D) Redox titration of MalE-TfcP. The 550-nm absorbance at 23 °C is plotted versus the solution potential and fitted to the Nernst equation. (E) Redox titration of MalE-TfcP following the EPR intensity at g = 2.26 of samples poised at indicated solution redox potentials.