TABLE 1

Competition binding data for [³H]N-methylspiperone sites at TM5 serine mutants

Values represent mean ± S.E.M. The expression of these receptors was as follows: WT: K_D, 0.58 nM; B_max, 4.8 pmol/mg; S5.42A: K_D, 0.59 nM; B_max, 4.0 pmol/mg; S5.43A: K_D, 1.4 nM; B_max, 20.7 pmol/mg; S5.46A: K_D, 0.50 nM; B_max, 2.3 pmol/mg.

Mutant	K_0.5
Mutant	WT	S5.42A	S5.43A	S5.46A
	nM
DNS	144 ± 17	660 ± 190	750 ± 370	330 ± 160
DNX	83 ± 5	2700 ± 990^*	770 ± 90	580 ± 340
DHX	490 ± 91	7400 ± 1000^*	2,600 ± 50	1600 ± 40
Quinpirole	365 ± 6	1040 ± 100	27,000 ± 10,000^*	2900 ± 820
Dopamine	450 ± 170	80,000 ± 3000^*	31,000 ± 6000^*	3500 ± 1,500

↵* Significantly different from WT (P < 0.05; one-way ANOVA and Tukey-Kramer Multiple Comparisons Test).