Table 2.
Summary of the metal and DNA binding affinities and allosteric coupling free energies for metalloderivatives of wild-type and E90A Bsu CsoR
| Bsu CsoR | metal | metal binding affinitya | DNA binding affinityb | Δ Gc | |
|---|---|---|---|---|---|
| (M-1) | K1 (M-1) | K2 (M-1) | (kcal/mol) | ||
| Wild-type | apo | - | 3.1 (±0.8) × 107 | 8.3 (±2.2) × 107 | - |
| Cu(I) | ≥ 1021 | 2.9 (±0.4) × 106 | ≤1.0 × 105 | ≥ +5.4 | |
| Co(II) | ≤ 105 | - | - | - | |
| Ni(II) | 3.6 (±0.3) × 109 | 5.7 (±1.0) × 106 | 3.1 (±0.5) × 107 | +1.6 (±0.3) | |
| Zn(II) | 1.6 (±0.1) × 108,c | 1.0 (±0.3) × 107 | 1.5 (±0.4) × 107 | +1.7 (±0.3) | |
| E90A | apo | - | 9.5 (±3.0) × 106 | 1.3 (±0.4) × 107 | - |
| Cu(I) | ≥ 1021 | 4.8 (±2.0) × 106 | 1.1 (±0.4) × 108 | -0.9 (±0.4) | |
a
The results of fitting to a simple 1:1 (metal:monomer) binding model.
b
Solution conditions: 10 mM MES, 0.4 M NaCl, 2 mM DTT, pH 6.5, 25 °C. We note that unique values of K1 and K2 are not readily resolved in this assay (see Methods)
c
A fit to two-site step-wise dimer binding models gives KZn1= 1.7 (±0.4) × 109 M-1; KZn2= 4.5 (±0.3) × 107 M-1 (see Supplementary Figure S1).