FIGURE 3.

Na⁺ dependence of ferredoxin:NAD⁺ oxidoreductase activity at A. woodii membranes. Ferredoxin-dependent NADH formation at A. woodii membranes was monitored at 340 nm in 20 mm Tris-HCl (pH 7.7), 2 mm DTE, and 2 μm resazurin in 3-fold distilled water. Shown are the effects of NaCl (■), KCl (▴), and LiCl (▾) on NADH formation. The data shown are representative of the results of three separate experiments using independent membrane preparations. Curve fitting and determination of the kinetic parameters K_m (Michaelis constant) and V_max (maximal enzyme velocity) were performed using GraphPad Prism Version 4.03 and the Michaelis-Menten equation (Y = (V_max × X)/(K_m + X)). Fd_red, reduced ferredoxin.