TABLE 3

Comparison of the ability of βγ dimers containing native or chimeric γ subunits to activate type II adenylyl cyclase

The EC50 and Vmax values obtained with each βγ dimer were determined by fitting each data set to sigmoid curves as described under Materials and Methods. Values are the average of three similar experiments expressed as means ± S.E.M.

Type II Adenylyl Cyclase
Type of Chimeras and βγ Dimers EC50Vmax
nM μmol / mg protein / min
Chimeras with activity similar to β1γ2
β1γ2 13.3 ± 1.2 29.05 ± 1.72
β1γBAA-S74L 15.6 ± 1.2§ 27.8 ± 1.74§
β1γBBA-S74L 18.2 ± 1.4§ 24.07 ± 1.85§
Chimeras with activity similar to β1γ1
β1γ1 46.7 ± 1.9 6.31 ± 0.65
β1γABB-L71S 48.7 ± 2.1§ 6.89 ± 1.09§
β1γAAB 61.8 ± 2.0* 9.13 ± 2.31*
β1γAAB-L71S 93.3 ± 11.9§ 25.91 ± 9.45§
β1γ1-S74L 33.1 ± 1.6§§ 8.39 ± 1.68
Chimeras with intermediate activity
β1γBAA 24.6 ± 1.3† 13.52 ± 1.11†
β1γBBA 35.7 ± 1.2†† 14.05 ± 1.07†
β1γ2-L71S 41.7 ± 1.3§ 16.19 ± 1.3§
β1γABB 25.2 ± 1.3* 23.17 ± 1.66††

  • ↵§ Significant differences in responses to βγ dimers containing γ subunits with altered CAAX sequence to direct modification with different prenyl groups with those containing γ subunits with native prenyl groups, p < 0.0001.

  • ↵* Significant differences in responses to βγ dimers in comparison with native β1γ2, p < 0.0001.

  • ↵§§ Significant differences in responses to βγ dimers containing γ subunits with altered CAAX sequence to direct modification with different prenyl groups with those containing γ subunits with native prenyl groups, p < 0.001.

  • ↵† Significant differences in responses to βγ dimers in comparison with native β1γ1, p < 0.0001.

  • ↵†† Significant differences in responses to βγ dimers in comparison with native β1γ1, p < 0.001.