TABLE 3.
Binding parameters of cysteine mutants of the secretin receptor in the absence or presence of CuP compared with wild-type and nondimerizing double-mutant secretin receptor
Values are expressed as means ± S.E.M. of data from three independent experiments.
|
pKi
|
Bmax
|
|||
|---|---|---|---|---|
| High-Affinity Site | Low-Affinity Site | High-Affinity Site | Low-Affinity Site | |
| pmol/mg | pmol/mg | |||
| WT | 8.62 ± 0.15 | 6.52 ± 0.19 | 7.2 ± 1.5 | 188 ± 3 |
| G243A/I247A | 8.14 ± 0.08* | 6.55 ± 0.22 | 9.7 ± 1.5 | 138 ± 36 |
| F240C | 9.31 ± 0.04 | 7.45 ± 0.03 | 0.4 ± 0.1 | 29 ± 5 |
| F240C (CuP) | 8.43 ± 0.18† | 7.25 ± 0.26 | 2.5 ± 0.8 | 21 ± 11 |
| G243C | 8.85 ± 0.18 | 6.84 ± 0.04 | 2.0 ± 0.7 | 84 ± 11 |
| G243C (CuP) | 8.80 ± 0.30 | 7.13 ± 0.20 | 2.0 ± 0.9 | 47 ± 11 |
| A246C | 9.46 ± 0.30 | 7.24 ± 0.14 | 0.6 ± 0.3 | 79 ± 10 |
| A246C (CuP) | 8.18 ± 0.23† | 7.35 ± 0.13 | 6.1 ± 2.1 | 58 ± 26 |
| I247C | 9.25 ± 0.16 | 7.14 ± 0.03 | 1.7 ± 0.9 | 104 ± 24 |
| I247C (CuP) | 8.93 ± 0.40 | 7.25 ± 0.31 | 3.2 ± 1.6 | 37 ± 1* |
| A250C | 8.87 ± 0.10 | 6.95 ± 0.14 | 2.7 ± 1.0 | 79 ± 12 |
| A250C (CuP) | 8.83 ± 0.05 | 7.13 ± 0.06 | 1.9 ± 0.3 | 60 ± 10 |
*
Significantly different from the wild-type receptor, P < 0.05.
†
Significantly different from the same receptor construct studied in the absence of cuprous phenanthroline, P < 0.05.