TABLE 3.
Concentrations of MgATP required for half-maximal binding by monomeric, dimeric, and oligomeric forms of NtrC
| Protein | Substrate | Oligomeric state | Concn for half-maximal binding of MgNTP (μM)a |
|---|---|---|---|
| MBP-NtrC | MgATP | Dimer | 180 ± 20 (5) |
| MBP-NtrCΔ444–469 | MgATP | Monomerb | 600 ± 80 (3) |
| MBP-NtrC | MgATPγS | Dimer | 170 (1) |
| P-MBP-NtrC | MgATPγS | >2 dimers | 155 ± 10 (4) |
a
Binding was assessed, and titration data were plotted to determine concentrations for half-maximal binding (see Materials and Methods). The number of independent titrations carried out for each NtrC protein is shown in parentheses, and standard deviations are indicated where appropriate. Proteins were unphosphorylated unless otherwise indicated (P-MBP-NtrC).
b
Gel filtration chromatography indicated that there was ≤20% residual dimer in the preparation (not shown).