Table 3

Effects of replacement of transmembrane domains of β1AR with corresponding regions of the β2AR on binding characteristics of norepinephrine

125I-CYPKdBmaxKiNorepinephrine
pM pmol/mg μM
β2AR26.6  ± 2.39.2  ± 0.518.0  ± 0.84
CH-130.5  ± 4.71.6  ± 0.516.0  ± 1.60c
CH-232.3  ± 7.55.6  ± 0.912.0  ± 1.60
CH-372.3  ± 23.613.7  ± 3.05.70  ± 0.693-a
CH-457.9  ± 20.710.8  ± 2.82.90  ± 0.45b
CH-569.7  ± 25.311.1  ± 3.21.80  ± 0.50b
CH-645.2  ± 14.42.8  ± 0.67.10  ± 1.50
CH-745.8  ± 9.40.47  ± 0.0419.0  ± 2.40d
CH-834.5  ± 4.40.067  ± 0.00427.0  ± 7.00d
β1AR50.5  ± 8.510.9  ± 0.82.00  ± 0.15

The binding of norepinephrine to the WT β2AR and β12-chimeric receptors were determined by competition with 50–100 pM 125I-CYP. The data were analyzed using the nonlinear least-squares regression computer program as described under Experimental Procedures. The results are shown as the mean ± S.E. from three to five separate experiments.

    • 3-a P < 0.05;bP < 0.01 compared with the WT β2AR; cP < 0.05;dP < 0.001 compared with the WT β1AR.