Table I.
Parameters from Fitting of kobs,1 versus Ligand Concentration Using Nonlinear Least Squares to Eq. (1) for Approach-to-Equilibrium Changes in PAI-1 Intrinsic Protein Fluorescence
| Metal | Buffer | Kd (μM) | k2 (s−1) | k−2 (s−1) |
|---|---|---|---|---|
| Cobalt | MOPS | 34 ± 13 | 0.22 ± 0.02 | 0.026 ± 0.013 |
| Nickel | MOPS | 38 ± 6 | 2.36 ± 0.09 | 0.074 ± 0.052 |
| Nickel | Tris | 32 ± 2 | 0.34 ± 0.01 | 0.015 ± 0.02 |
| Copper | Tris | 0.086 ± 0.027 | 4.4 ± 0.4 | −0.29 ± 0.51 |
Kd, k2, and k−2 represent the dissociation constant for the initial binding and forward and reverse rates for the subsequent conformational change that occurs in PAI-1 upon metal binding, as shown in Scheme 1. Errors shown come directly from the fit.