Table 1.
Binding Characteristics |
Intracellular Calcium Response |
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Agonists |
Antagonists |
Agonists |
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Constructs | CCK |
1,5-Benzodiazepine #1d |
L-364,718 |
SR-27897 |
CCK |
1,5-Benzodiazepine #1d |
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Ki | Bmax | Ki | Bmax | Ki | Bmax | Ki | Bmax | EC50 | Emax | EC50 | Emax | |
nM | pmol/mg protein | nM | pmol/mg protein | nM | pmol/mg protein | nM | pmol/mg protein | nM | nM | nM | nM | |
WT | 0.5 ± 0.1 | 0.7 ± 0.1 | 4.6 ± 0.3 | 10.3 ± 0.2 | 4.7 ± 1.2 | 14.1 ± 1.4 | 5.3 ± 1.0 | 22.9 ± 3.9 | 0.03 ± 0.01 | 236 ± 30 | 6.1 ± 0.4 | 213 ± 26 |
K187A | 0.4 ± 0.1 | 0.6 ± 0.2 | 4.7 ± 0.3 | 9.0 ± 1.1 | 1.1 ± 0.1 | 12.0 ± 2.5 | 3.1 ± 0.6 | 20.4 ± 3.0 | 0.1 ± 0.1 | 232 ± 39 | 122 ± 30 | 198 ± 37 |
K187D | 0.4 ± 0.1 | 0.5 ± 0.1 | 4.7 ± 0.7 | 9.9 ± 1.1 | 3.2 ± 0.5 | 12.5 ± 1.7 | 2.7 ± 0.4 | 18.8 ± 0.7 | 7.0 ± 1.0 | 120 ± 29 | N.D. | N.D. |
WT)31–429 | 0.7 ± 0.1 | 5.7 ± 1.5 | 4.3 ± 0.5 | 4.7 ± 1.3 | 0.13 ± 0.03 | 228 ± 32 | 7.6 ± 1.8 | 191 ± 39 | ||||
K187D)31–429 | 0.9 ± 0.1 | 1.4 ± 0.4 | 7.7 ± 2.2 | 1.4 ± 0.4 | 0.16 ± 0.04 | 240 ± 46 | 25.4 ± 4.0 | 175 ± 40 | ||||
D5K | 1.3 ± 0.2 | 10.0 ± 1.9 | 4.3 ± 0.9 | 4.6 ± 1.5 | 0.29 ± 0.06 | 100 ± 24 | 9.0 ± 2.0 | 105 ± 27 | ||||
D5K(K187D) | 1.6 ± 0.2 | 7.9 ± 2.0 | 4.5 ± 0.9 | 1.4 ± 0.2 | 0.03 ± 0.01 | 102 ± 28 | 28.8 ± 5.6 | 96 ± 19 |
Shown are Ki and Bmax values for ligand binding to membranes prepared from cells expressing each of the noted CCK receptor constructs. Shown also are EC50 and Emax values (delta changes from basal values, nM) for ligand-stimulated intracellular calcium responses in these cells. All values represent the means ± S.E.M. of data from at least three independent experiments. N.D., not detected.