Table 3.
Summary of functional characteristics of single LHR mutants
| Mutant | Bamax (% wt) | Kbd (mut/wt) | Basal cAMPb (mut/wt) | ECb50 (mut/wt) | Ramax (% wt) | Qb (mut/wt) |
|---|---|---|---|---|---|---|
| H2 | ||||||
| N400W (n = 3) | 32 ± 10 | 0.6 ± 0.1 | 0.9 ± 0.1 | 3.3 ± 0.9 | 81 ± 7 | 1.0 ± 0.05 |
| D405N (n = 3) | 143 ± 15 | 1.6 ± 0.1 | 1.0 ± 0.2 | 4.4 ± 1.5 | 28 ± 2 | 0.1 ± 0.01 |
| H4 | ||||||
| W491N (n = 4) | 35 ± 9 | 1.1 ± 0.3 | 0.6 ± 0.2 | 3.2 ± 0.5 | 78 ± 22 | 0.9 ± 0.05 |
| H6 | ||||||
| K570N (n = 3) | 90 ± 23 | 0.9 ± 0.1 | 0.7 ± 0.1 | 2.1 ± 0.8 | 110 ± 28 | 0.5 ± 0.06 |
| D578H (n = 5) | 116 ± 16 | 0.9 ± 0.1 | 22.0 ± 4.0c | ND | NR | ND |
| H7 | ||||||
| N615A (n = 3) | 46 ± 14 | 0.8 ± 0.01 | 1.0 ± 0.1 | 5.6 ± 0.1 | 18 ± 7 | 0.1 ± 0.01 |
| N615D (n = 5) | 34 ± 7 | 1.7 ± 0.2 | 0.8 ± 0.1 | 3.0 ± 0.1 | 8 ± 1 | 0.3 ± 0.08 |
| N615K (n = 2) | 144 ± 5 | 1.5 ± 0.1 | 1.0 ± 0.2 | 5.6 ± 0.2 | 47 ± 8 | 0.2 ± 0.03 |
| N619A (n = 5) | 20 ± 6 | 0.5 ± 0.1 | 0.8 ± 0.1 | ND | 2 ± 0.3 | ND |
| N619D (n = 3) | 97 ± 38 | 0.8 ± 0.2 | 4.6 ± 1.5c | 1.2 ± 0.3 | 32 ± 6 | 0.3 ± 0.03 |
| N619K (n = 3) | 36 ± 12 | 0.4 ± 0.1 | 1.6 ± 0.3c | ND | 3 ± 1 | ND |
| Y623A (n = 2) | 12 ± 5 | 0.5 ± 0.1 | 0.7 ± 0.0 | ND | NR | ND |
NR Not responsive, ND not determined
aGiven as a percentage of that of wild-type LHR
bPresented as the ratio of the parameter to that of the wild-type LHR, where Q is the coupling efficiency as defined in the text. Mean values ± SEM of the wild-type LHR were (n = 22): Bmax = 61.9 ± 15.2 fmol/well; Kd = 1.8 ± 0.25 nM; Basal cAMP = 2.6 ± 0.34 pmol/well; EC50 = 0.5 ± 0.1 nM; Rmax = 217.2 ± 38.6 pmol/well
cIf normalized to expression levels, the values for basal cAMP for D578H, N619D and N619 K are, respectively, 22.8 ± 3.8, 6.0 ± 1.2 and 5.1 ± 0.7