Table 1.
Ligand binding affinities of the designs
| Site | Kd Zn − Malt. | Kd Zn + Malt. | Kd Malt. − Zn | Kd Malt. + Zn |
|---|---|---|---|---|
| A1 | 56 ± 5 | 56 ± 5 | nb | nb |
| A2 | 135 ± 4 | 135 ± 4 | nb | nb |
| B1 | nb | 5 ± 1 | 0.9 ± 0.05 | 5 ± 0.3 |
| B2 | nb | 1.4 ± 0.3 | 500 ± 12 | 150 ± 7 |
| WT | nb | nb | 0.8 ± 0.03 | 0.8 ± 0.03 |
The A sites show changes in fluorescence in response to zinc but not maltose (1 mM). The B sites show changes in fluorescence in response to maltose, but not zinc (10 mM). The zinc-mediated change in fluorescence of the A sites is not modulated by the presence of maltose. The maltose-mediated changes in fluorescence in the B sites are modulated by the presence of zinc. All Kd values are reported in μM. WT, wild-type MBP; nb, no binding; Malt., maltose.