TABLE 1.

Initial rates of transport measured in HeLa cells

The initial rates of transport (10 min) were measured in HeLa cells expressing the wild type or indicated mutants as described under “Experimental Procedures” and expressed in terms of total cell protein. The percentage of activity at zero Cl⁻ was calculated relative to that at maximal Cl⁻ (100 mm). β-CIT binding was measured in similar cells. The K_m for Cl⁻ was calculated for functional Cl⁻-dependent mutants using a concentration range of Cl⁻ and isethionate as a replacement. Each value represents the mean and S.E. of three to five independent experiments for the K_m measurements and two to four independent experiments for the transport or binding activity measurements. Each experiment was performed in triplicate or quadruplicate wells.

rSERT	5-HT influx		β-CIT binding	Km for Cl−
	0 mm [Cl−]	100 mm [Cl−]
	pmol/mg/min		% of wild type	mm
Wild type	0.045 ± 0.009	0.99 ± 0.1	100 ± 2	5 ± 1
S336D	0.055 ± 0.005	0.06 ± 0.007	30 ± 3
S336E	0.005 ± 0.002	0.009 ± 0.003	12 ± 1
S336V	0.004 ± 1E-3	0.004 ± 0.001	49 ± 2
S336A	0.005 ± 0.002	0.03 ± 0.002	87 ± 2
S336C	0.06 ± 0.02	0.12 ± 0.05	93 ± 3
Y121F	0.032 ± 0.003	0.79 ± 0.01	93 ± 3	15 ± 3
Y121I	0.007 ± 0.002	0.05 ± 0.01	38 ± 3	55 ± 4
Y121L	0.007 ± 0.003	0.03 ± 0.01	49 ± 1
Y121E	0.004 ± 0.001	0.01 ± 0.004	17 ± 2
N368A	0.013 ± 0.003	0.08 ± 0.007
C369D	0.021 ± 0.004	0.05 ± 0.001	14 ± 2
C369E	0.022 ± 0.008	0.085 ± 0.027	54 ± 7	17 ± 5
C369A	0.05 ± 0.01	1 ± 0.06	100 ± 6	10 ± 2
C369S	0.1 ± 0.011	1.34 ± 0.08	96 ± 10	9 ± 2
Q332E	0.006 ± 0.002	0.018 ± 0.002	98 ± 6
Q332L	0.001 ± 0.000	0.027 ± 0.002	100 ± 2
Q332V	0.010 ± 0.002	0.069 ± 0.020	88 ± 6
Q332C	0.015 ± 0.003	0.109 ± 0.04	95 ± 7	42 ± 7
Q332N	0.002 ± 0.000	0.011 ± 0.002