TABLE 2 .
Dissociation constants determined by isothermal titration calorimetrya
| Protein target | Ligand | Kd (µM)b | Phosphotransfer and phosphatase specificity |
|---|---|---|---|
| CrdS | CrdA | 1.41 ± 0.33 | Yes |
| CrdS | FrgC | >75 | |
| CrdS | NtrC1189 | >75 | |
| CrdS | T. maritima RR468 | >75 | |
| FrgB | CrdA | >75 | |
| FrgB | FrgC | 1.23 ± 0.37 | Yes |
| FrgB | NtrC1189 | >75 | |
| FrgB | T. maritima RR468 | >75 | |
| HK1190 | CrdA | >35 | |
| HK1190 | FrgC | >35 | |
| HK1190 | NtrC1189 | 1.23 ± 0.37 | Yes |
| HK1190 | T. maritima RR468 | >55 | |
| T. maritima HK853 | CrdA | >75 | |
| T. maritima HK853 | FrgC | >55 | |
| T. maritima HK853 | NtrC1189 | >55 | |
| T. maritima HK853 | T. maritima RR468 | 1.16 ± 0.18 | Yes |
| CrdS6 | CrdA | >75 | |
| CrdS6 | NtrC1189 | 2.09 ± 1.11 | Yes |
a
Binding affinities (dissociation constants) for 4 distinct TCS HK-RR protein interactions, with cognate and noncognate partners, were determined by ITC. Cognate TCS pairs that were found to interact and display phosphotransfer and phosphatase specificity are in bold. Noncognate proteins were found to have Kd values above the upper limit detectable in this assay.
b
Values are the averages of four separate measurements (± standard deviations).