CCK-8 binding affinities of the wild type CCKB (CCKBR-WT) and amino-terminal/TMI mutant CCKB receptors
| Kd | Fmut (Kdmut/Kd CCKBR-WT) | |
|---|---|---|
| nm | ||
| CCKBR-WT | 0.46 ± 0.08 | 1.0 |
| CCKBR-E51A | 0.57 ± 0.17 | 1.2 |
| CCKBR-L52A | 0.50 ± 0.22 | 1.0 |
| CCKBR-E53A | 0.94 ± 0.05 | 2.0 |
| CCKBR-M54A | 0.74 ± 0.21 | 1.5 |
| CCKBR-A55L | 0.30 ± 0.17 | 0.6 |
| CCKBR-I56A | 0.99 ± 0.20 | 2.1 |
| CCKBR-R57A | 9.96 ± 0.48 | 21.3 |
| CCKBR-I58A | 0.60 ± 0.33 | 1.2 |
Inhibition of 125I-BH-CCK-8 binding by increasing concentrations of unlabelled CCK-8 was performed on CCKBR-WT and mutant receptors transiently expressed in COS-1 cells. The dissociation constants (K d) were determined using the nonlinear least-squares curve-fitting program, LIGAND (19) and are expressed as the mean ± standard error of three to nine experiments performed in duplicate. The factor Fmut represents the effect of the mutations on CCK-8 affinity and is calculated as theK d of the mutated receptor divided by theK d of the CCKBR-WT.