FIGURE 7.

EDTA sensitivity of intermediates in the cobalt binding reaction. (A) Fluorescence time courses observed for reaction of apo-MnSOD (50 μg/mL in 20 mM MOPS, pH 7, 45°C) with reaction initiated by addition of CoCl₂ and subsequently interrupted by addition of EDTA to a final concentration of 80 μM. (B) Decomposition of the fluorescence time course observed for addition of EDTA 1 min after initiating cobalt uptake. Raw data (top trace) was decomposed into a single exponential relaxation plus a linear term (lower traces). The residuals resulting from the fit are shown below. (C) Variation of rate constant for cobalt extraction by EDTA with time. The values of k_EDTA from analysis of the kinetic traces (open circles) is shown together with the regression line for a constant value (k_EDTA = 0.75 min⁻¹).