Fig. 7.

³H-cAMP accumulation in response to CGP12177 (A, C, and E), and pindolol (B, D, and F) in transiently transfected cells expressing β₁-V189T (A and B), β₁-L195Q (C and D), and β₁-W199Y (E and F). The CGP12177 responses were examined in the absence and presence of 3, 10, and 30 nM cimaterol. Bars represent basal ³H-cAMP accumulation, that in response to 10 µM isoprenaline or that in response to 3, 10, and 30 nM cimaterol alone. Data points are mean ± S.E.M. of triplicate determinations. These single experiments are representative of (A) six, (B) five, (C) three, (D) three, (E) four, and (F) four separate experiments. This figure shows that both the “dip” in the CGP12177 + cimaterol curve and biphasic pindolol response are still present at the β₁-V189T, suggesting conservation of the secondary conformation. However, both are reduced at β₁-L195Q and β₁-W199Y, suggesting some loss of the secondary conformation at β₁-L195Q and β₁-W199Y (see Fig. 6A for β₁-WT comparison).