Table 5

Effects of replacement of amino acids in TM2 of the β2AR with alanine on ligand-binding characteristics of the β2AR

125I-CYPLigands (Ki)
KdBmaxFormoterolProcaterolSalmeterol
pM pmol/mg nM
WT β2AR24.4  ± 4.10.6  ± 0.0638  ± 10150  ± 77.4  ± 3.3b
T73A-38.6  ± 5.63.5  ± 0.343  ± 7160  ± 77.7  ± 2.2
C77A-24.0  ± 2.50.9  ± 0.153  ± 4220  ± 124.5  ± 1.2
H93A-19.0  ± 32.91.1  ± 0.0590  ± 31540  ± 1105-a 5.8  ± 1.7
I94A-23.9  ± 4.51.0  ± 0.0951  ± 10340  ± 225.2  ± 0.9
L95A-20.1  ± 3.00.3  ± 0.0445  ± 3170  ± 144.4  ± 1.9
M96A-26.7  ± 2.61.3  ± 0.148  ± 6200  ± 209.7  ± 2.1
K97A-18.1  ± 3.60.3  ± 0.0637  ± 14120  ± 86.1  ± 1.4
M98A-26.5  ± 2.20.5  ± 0.0450  ± 13250  ± 928.7  ± 4.9

The binding of ligands to the WT β2AR and alanine-substituted β2AR mutants were determined by competition with 50 pM125I-CYP. The data were analyzed using the nonlinear least-squares regression computer program as described underExperimental Procedures. The results are shown as the mean ± S.E. from three to four separate experiments.

    • 5-a P < 0.01 compared with the WT β2AR; b The data are taken from Table 4 for comparison.