TABLE 10.
Ki, IC50, and dose ratio values for antagonist binding to strains overexpressing Sst2p
| STE2 allele | Antagonist | Ki (for binding) | IC50 (for binding) | EC50 | Expected dose ratioa | Measured dose ratiob | Expected/observed dose ratio |
|---|---|---|---|---|---|---|---|
| nm | nm | nm | |||||
| Chromosomal (A4757) | Agonist | 46 ± 20 | |||||
| +3 μm d-Tyr3 | 850 ± 65 | 338 ± 108 | 19 ± 8c | 18 | |||
| +3 μm dTA | 425 ± 12 | 333 ± 62 | 9 ± 4c | 36 | |||
| +3 μm dTH | 2350 ± 1340 | 174 ± 48 | 51 ± 36c | 3 | |||
| CEN-STE2 (A4744) | +5 μm d-Tyr3 | 9 ± 3 | 22 ± 7 | NDd | ND | ND | |
| +5 μm dTA | 9 ± 2 | 22 ± 3 | ND | ND | ND | ||
| +5 μm dTH | 17 ± 5 | 43 ± 11 | ND | ND | ND | ||
| Multicopy STE2 (A4746) | Agonist | 430 ± 190 | |||||
| +5 μm d-Tyr3 | 8 ± 2 | 17 ± 5 | 1240 ± 350 | 643 ± 182 | 3 ± 1.5 | 223 | |
| +5 μm dTA | 22 ± 7 | 50 ± 14 | 400 ± 30 | 226 ± 68 | 1 ± 0.4 | 240 | |
| +5 μm dTH | 25 ± 6 | 56 ± 12 | 3820 ± 550 | 200 ± 47 | 9 ± 4 | 22 |
a The expected dose ratio = DRbind = 1 + [antagonist]/Ki.
b The measured dose ratio = DRsig = EC50 in the presence of antagonist/EC50 in the absence of antagonist.
c The measured dose ratios for the strain expressing chromosomal Ste2p were calculated with 3 μm antagonists instead of 5 μm, because we were unable to saturate downstream responses with strains overexpressing Sst2p with mixtures of agonist and antagonist. The expected dose ratios were also calculated for 3 μm concentrations.
d ND means not determined.