Table 3

Binding parameters of WT, B2, and B3 stable lines

Saturation Binding
	[³H]Yohimbine	[¹²⁵I]PIC
	B_max	B_max		K_d
	B_max	−GppNHp	+GppNHp	−GppNHp	+GppNHp
	pmol/mg protein		nM
WT	19 ± 2	3.2 ± 0.7	1.5 ± 0.6	0.8 ± 0.1	1.4 ± 0.3
B2	36 ± 3	1.9 ± 0.5	1.2 ± 0.5	1.2 ± 0.3	2.2 ± 0.7
B3	34 ± 4	1.7 ± 0.7	0.8 ± 0.3	1.4 ± 0.3	1.9 ± 0.3

Saturation binding to membranes from CHO-K1 cells expressing WT and mutant α_2a-AR was performed in 96-well plates. Membranes were incubated with 1 to 40 nM [³H]yohimbine or 0.1 to 4 nM [¹²⁵I]PIC for 30 to 45 min at room temperature. [¹²⁵I]PIC binding was done in the presence or absence of 10 μM GppNHp. Data represent the mean ± S.E. of four or five separate experiments performed in duplicate.