FIGURE 2.

UV-visible spectra of CBS. The spectra were recorded in 50 mm Tris buffer, pH 8.6, at room temperature using 8 μm wild-type CBS (A), 8 μm T257M (B), and 10 μm T257IM (C), T257S (D), T257V (E), T260M (F), T260S (G), and T260V (H) inside an anaerobic glove box. Wild-type ferric CBS exhibits a Soret peak at 428 nm (black), which shifts to 449 nm (blue) upon reduction with dithionite. The ferrous-CO species has a Soret maximum at 420 nm (olive), which returns to 428 nm (red) upon overnight air oxidation of wild-type, to 425 nm with T257S, T260M, and T260V, or to 426 nm with T260S CBS and remains at 420 nm with T257I, T257M, and T257V.