Table 1.
High affinity dissociation equilibrium constants (KD) estimated from fluorescence anisotropy data.†
| Transporter | KD | error |
|---|---|---|
| BtuB apo | 61 nM | ± 5 nM |
| BtuB +Ca2+B12 | 26 nM | ± 2 nM |
| FhuA apo | 64 nM | ± 4 nM |
| FhuA +FeChr | 38 nM | ± 3 nM |
| BtuB + ColE3R | 1.5μM | ± 0.2μM |
†
Errors given are standard errors based upon the fits to the data using Eqn. 1. See Experimental Procedures. In each case, the data were fit with n values that ranged from 1 to 1.5. Non-specific binding was detected at higher transporter concentrations (ca. > 10μM), and data taken at these higher concentrations was not used in the analysis.