Table 1.

ATP pharmacology of alanine-substituted mutants

n /basal (pA/pF) EC50 (μm) pEC50nHYmax (pA/pF) (Ymax//30μm) Δ(ΔG) (kcal/mol)
Mock 4 1.96 ± 0.62 0 ± 0
WT 26 0.75 ± 0.08 5.25 5.28 ± 0.07 1.76 ± 0.17 420 ± 36 1.15 ± 0.05
TM1
G30A 7 0.81 ± 0.16 3.98 5.40 ± 0.06 1.64 ± 0.27 268 ± 43 1.05 ± 0.02 0.16 ± 0.08
F31A 7 0.60 ± 0.03 4.27 5.37 ± 0.03 1.88 ± 0.21 444 ± 36 1.04 ± 0.02 0.13 ± 0.04
V32A 6 0.75 ± 0.07 11.75 4.93 ± 0.07 2.00 ± 0.21 173 ± 14 1.26 ± 0.13 −0.48 ± 0.10
H33A 7 0.93 ± 0.09 1.18 5.93 ± 0.07** 2.21 ± 0.32 197 ± 48 0.98 ± 0.02 0.88 ± 0.10
R34A 6 0.78 ± 0.08 13.04 4.86 ± 0.04 2.00 ± 0.24 27 ± 12** 1.49 ± 0.21 −0.59 ± 0.06
M35A 7 0.83 ± 0.06 7.08 5.15 ± 0.09 1.45 ± 0.12 213 ± 62 1.19 ± 0.09 −0.17 ± 0.12
V36A 6 0.86 ± 0.12 5.37 5.27 ± 0.06 1.64 ± 0.21 357 ± 71 1.08 ± 0.04 0.01 ± 0.08
Q37A 7 0.85 ± 0.15 33.11 4.48 ± 0.04** 1.85 ± 0.13 203 ± 24 1.95 ± 0.21 −1.08 ± 0.06
L38A 5 0.64 ± 0.03 5.50 5.26 ± 0.02 2.09 ± 0.24 298 ± 39 1.07 ± 0.04 0.03 ± 0.02
L39A 5 0.51 ± 0.04 6.03 5.22 ± 0.09 2.15 ± 0.18 311 ± 49 1.05 ± 0.04 0.08 ± 0.13
I40A 5 1.19 ± 0.09 0.96 6.02 ± 0.07** 2.07 ± 0.23 209 ± 68 1.02 ± 0.02 1.01 ± 0.08
L41A 5 0.83 ± 0.09 15.14 4.82 ± 0.06* 1.77 ± 0.07 218 ± 20 1.31 ± 0.08 −0.63 ± 0.08
L42A 7 0.90 ± 0.05 3.89 5.41 ± 0.12 1.67 ± 0.16 384 ± 84 1.12 ± 0.07 0.17 ± 0.16
Y43A 9 39.54 ± 10.03** 0.35 6.46 ± 0.19** 1.37 ± 0.62 270 ± 52 1.01 ± 0.01 1.60 ± 0.26
F44A 9 48.99 ± 7.94** 0.60 6.22 ± 0.20** 2.06 ± 0.30 312 ± 17 0.99 ± 0.02 1.29 ± 0.28
V45A 6 1.02 ± 0.17 nd nd nd 4 ± 1** nd nd
W46A 6 0.98 ± 0.14 7.76 5.11 ± 0.04 1.55 ± 0.17 399 ± 57 1.07 ± 0.05 −0.22 ± 0.05
Y47A 5 1.23 ± 0.16 nd nd nd 2 ± 0** nd nd
V48A 6 1.01 ± 0.06 3.98 5.40 ± 0.06 1.65 ± 0.13 218 ± 18 1.02 ± 0.01 0.16 ± 0.08
F49A 6 1.04 ± 0.11 5.88 5.23 ± 0.10 2.14 ± 0.36 272 ± 68 1.04 ± 0.02 −0.07 ± 0.13
I50A 7 1.03 ± 0.03 27.54 4.56 ± 0.04** 1.88 ± 0.15 225 ± 89 1.91 ± 0.19 −0.98 ± 0.03
V51A 5 1.15 ± 0.14 nd nd nd 2 ± 0** nd nd
Q52A 6 0.56 ± 0.14 10.72 4.97 ± 0.07 2.20 ± 0.43 275 ± 41 1.16 ± 0.02 −0.42 ± 0.10
K53A 7 0.63 ± 0.09 8.91 5.05 ± 0.04 2.31 ± 0.20 206 ± 53 1.10 ± 0.04 −0.32 ± 0.06
S54A 6 0.77 ± 0.12 8.32 5.08 ± 0.09 1.79 ± 0.31 206 ± 79 1.17 ± 0.07 0.27 ± 0.12
TM2
I328A 6 0.74 ± 0.11 0.62 6.21 ± 0.11** 1.70 ± 0.22 272 ± 52 0.99 ± 0.02 1.26 ± 0.15
P329A 9 1.22 ± 0.11 1.70 5.77 ± 0.06** 1.62 ± 0.29 416 ± 69 1.04 ± 0.02 0.70 ± 0.11
T330A 6 0.97 ± 0.11 3.55 5.45 ± 0.10 1.93 ± 0.30 286 ± 99 1.07 ± 0.05 0.23 ± 0.14
I331A 6 0.99 ± 0.10 4.57 5.34 ± 0.08 1.97 ± 0.25 305 ± 35 1.01 ± 0.02 0.08 ± 0.10
I332A 5 0.94 ± 0.09 3.55 5.45 ± 0.06 1.91 ± 0.18 245 ± 70 1.02 ± 0.02 0.23 ± 0.09
N333A 9 1.22 ± 0.06 1.07 5.97 ± 0.07** 1.57 ± 0.10 339 ± 44 1.01 ± 0.01 0.94 ± 0.09
L334A 6 0.71 ± 0.07 4.37 5.36 ± 0.10 1.23 ± 0.10 363 ± 67 1.08 ± 0.05 0.11 ± 0.13
T336A 6 0.76 ± 0.08 5.62 5.25 ± 0.14 1.67 ± 0.15 222 ± 47 1.09 ± 0.05 −0.05 ± 0.19
L338A 12 1.01 ± 0.08 27.54 4.56 ± 0.07** 1.66 ± 0.22 283 ± 20 2.39 ± 0.30 −0.98 ± 0.10
T339A 7 1.19 ± 0.10 1.55 5.81 ± 0.07** 1.98 ± 0.21 370 ± 56 1.01 ± 0.01 0.72 ± 0.09
S340A 9 0.87 ± 0.06 19.50 4.71 ± 0.06** 2.38 ± 0.15 211 ± 3 1.61 ± 0.14 −0.78 ± 0.09
I341A 10 1.96 ± 0.13 7.59 5.12 ± 0.09 1.94 ± 0.07 229 ± 32 1.26 ± 0.13 −0.22 ± 0.13
G342A 18 1.24 ± 0.19 26.30 4.59 ± 0.04** 1.68 ± 0.12 289 ± 33 2.04 ± 0.15 −0.95 ± 0.06
V343A 10 1.80 ± 0.09 0.66 6.18 ± 0.07** 1.41 ± 0.13 301 ± 68 1.00 ± 0.01 1.23 ± 0.10
G344A 14 1.11 ± 0.17 66.07 4.18 ± 0.07** 1.68 ± 0.14 251 ± 39 2.76 ± 0.26 −1.50 ± 0.10
S345A 11 0.83 ± 0.16 15.49 4.81 ± 0.07** 1.44 ± 0.13 236 ± 5 1.47 ± 0.09 −0.64 ± 0.10
F346A 10 0.88 ± 0.12 6.46 5.19 ± 0.10 1.88 ± 0.12 397 ± 48 1.09 ± 0.04 −0.12 ± 0.14
L347A 6 1.01 ± 0.03 12.02 4.92 ± 0.08 1.79 ± 0.16 217 ± 48 1.31 ± 0.09 −0.49 ± 0.10
C348A 7 1.02 ± 0.09 10.72 4.97 ± 0.08 1.72 ± 0.20 457 ± 28 1.25 ± 0.15 −0.43 ± 0.10
D349A 5 1.21 ± 0.14 nd nd nd 3 ± 1** nd nd
W350A 8 0.87 ± 0.07 8.51 5.07 ± 0.09 1.81 ± 0.12 278 ± 35 1.18 ± 0.09 −0.29 ± 0.12
I351A 6 1.03 ± 0.13 9.77 5.01 ± 0.06 2.21 ± 0.32 246 ± 49 1.13 ± 0.06 −0.37 ± 0.08
L352A 9 0.85 ± 0.10 8.32 5.08 ± 0.05 2.11 ± 0.07 276 ± 38 1.11 ± 0.03 −0.27 ± 0.07
L353A 6 1.12 ± 0.14 9.12 5.04 ± 0.08 2.03 ± 0.16 223 ± 39 1.08 ± 0.04 −0.32 ± 0.11
  • Data from experiments like those shown in Figure 1./basal is the holding current measured in the absence of agonist; all other parameters are defined in Results./basal and Ymax of Y43A and F44A were determined in one set of experiments, and EC50, nH, and Ymax//30 μm were determined in another, also as described in Results. Mock, Cells expressing only GFP; n, the number of times that complete concentration-response curves were generated in single cells; nd, not determined. We did not test for differences in Ymax//30μm or Δ(ΔG). The average cell capacitance was 14.6 ± 0.5 pF (n = 100).

    *p < 0.05; **p < 0.01.