TABLE 5.
Binding of wild-type and mutant CodY proteins to the ilvB promoter regiona
| CodY protein | Approximate Kd (nM) for binding to ilvB site II |
||
|---|---|---|---|
| No effectors | GTP (4 mM) | BCAAs (10 mM) | |
| Wild-type | 400-800 | 50-100 | 25-50 |
| F98A | ∼400 | 50-100 | ∼200 |
| F71E | 400-800 | 85-100 | >160b |
| F40A | ∼400 | 50-100 | >100b |
| R61A | ∼320 | ∼50 | ∼160 |
a
The results presented reflect analyses of DNase I footprinting experiments displayed in Fig. 2 to 6 and other experiments (not shown) in which the concentration of CodY was varied but the concentrations of the effectors (when present) were saturating. The CodY concentration that gave 50% protection was taken to be an approximation of the Kd for binding.
b
At the concentrations shown, F71E CodY and F40A CodY were not able to bind to the ilvB probe at BCAA concentrations as high as 40 mM. Higher concentrations of mutant CodY were not tested.