Escherichia coli RIC Is Able to Donate Iron to Iron-Sulfur Clusters
Figure 1
Formation of Fe-S clusters in apo-ferredoxin mediated by RIC.
A. UV-Visible spectra of ferredoxin upon incubation, under anaerobic conditions, of apo-ferredoxin (25 µM) with RIC (50 µM), IscS (2.5 µM), and L-cysteine (3 mM) for 15, 30 and 75 min (from bottom to top). Spectra are offset for clarity and the top bold-line spectrum corresponds to the commercial spinach holo-ferredoxin. B. EPR spectra of reduced holo-ferredoxin (30 µM) (trace a) and of reconstitution reactions of apo-ferredoxin (30 µM) achieved in 20 mM Tris-HCl plus 150 mM NaCl, pH 7.5 buffer containing 4 mM DTT, 2 µM IscS and 2 mM L-cysteine using as iron source 300 and 100 µM E. coli RIC (traces b and c, respectively) and 200 µM ferrous iron (trace d). The spectra of the reaction mixture prepared as in b but lacking the apo-ferredoxin (trace e) or done with apo-RIC (trace f) are also presented. Spectra were recorded at 9.34 MHz microwave frequency, 2.0 mW microwave power, 1 mT modulation amplitude and temperature 17 K.