Figure 3.

Electronic absorption spectroscopy of EcFeoC species suggests the presence of [Fe-S] clusters. A. Absorption spectrum of the MBP-EcFeoC fusion protein aerobically as-isolated. B. Absorption spectrum of the cleaved apo EcFeoC protein. C. Absorption spectrum of the cleaved, anaerobically reconstituted EcFeoC protein. Solutions were kept at room temperature in a UV-transparent cuvette, and protein concentrations were generally 1 μmol/L to 20 μmol/L. Sample A was in MBP elution buffer, sample B was in TEV cleavage buffer, and sample C was in anaerobic reconstitution buffer (see Materials and Methods). Absorption data are normalized to the most intense band corresponding to the protein absorbance (280 nm), and each inset displays the full spectrum of each sample.