Molar ellipticity values of far-UV signals (190 and 220 nm) are obtained from difference CD spectra (Figures 2C,E,G ) and indicate secondary structure in the N-terminal domain. Its tertiary structure and impact on the heme center are suggested by molar ellipticity values of near-UV (286 nm) and Soret (413 nm) signals, respectively, from CD spectra (Figures 2B,F,H ). All Molar ellipticity values are presented in deg*cm2/dmol. N/A: not applicable. Table S1 . Crystallographic data for RLF.