TABLE 6.
Evaluation of differences between binding and signaling assays
| Kd | Relative Bmaxa | Nsb | Absolute IC50 (for binding) | |
|---|---|---|---|---|
| nm | au | nm | ||
| pH values | ||||
| 3.5 | 4 ± 1 | 1 | 0.03 ± 0.02 | 50 ± 5 |
| 4.0 | 7 ± 1 | 1 ± 0.05 | 0.01 ± 0.01 | 40 ± 1 |
| 4.6 | 6 ± 1 | 0.9 ± 0.06 | 0.02 ± 0.01 | 30 ± 9 |
| Binding condition | ||||
| Acetate buffer (0 °C) | 12 ± 2 | 1 | 0.02 ± 0.01 | 15 ± 6 |
| Media (0 °C) | 4 ± 0.5 | 1 ± 0.08 | 0.03 ± 0.01 | NDc |
| Media (30 °C) | 12 ± 0.6 | 3.5 ± 0.3d | 0.2 ± 0.03 | 6 ± 2 |
a au indicates arbitrary fluorescence units.
b Ns indicates non-specific binding.
c ND means not determined.
d The increased Bmax is a result of internalization of the agonist-bound receptor and transit of newly synthesized receptors to the cell surface at 30 °C.