FIGURE 5.

Representative dose-response curves of the three WT GpHRs and selected mutants. These studies were done in HEK 293T cells, and cAMP was measured by a colorimetric assay at 405 nm based on the conversion of o-nitrophenyl-β-d-galactopyranoside into o-nitrophenol. The reaction is catalyzed by cAMP activation of a β-galactosidase gene under the control of a human vasoactive intestinal peptide promoter containing five cAMP-response elements. The results were compared with the activation achieved by 10 μm forskolin and are expressed in arbitrary units (AU). b is bovine.