Table 1.

Transport and binding activities of cytoplasmic cysteine mutants

Mutation	Original residue	Domain	% of C109A
Mutation	Original residue	Domain	Transport activity	Binding activity
X8C^1-a			32 ± 4	56 ± 6
X8C/21C^1-a	C	N terminus	30 ± 3	47 ± 6
X8C/15C,21C^1-a	C,C	N terminus	27 ± 2	50 ± 5
X8C/137C	L	IL1	52 ± 1	41 ± 5
X8C/138C	A	IL1	Inactive	Inactive
X8C/143C	H	IL1	Inactive	Inactive
X8C/145C	N	IL1	Inactive	Inactive
X8C/147C^1-a	C	IL1	33 ± 2	70 ± 9
X8C/155C^1-a	C	IL1	79 ± 3	48 ± 2
X8C/157C	I	IL1	26 ± 1	61 ± 5
X8C/277C	S	IL2	26 ± 8	28 ± 1
X8C/357C^1-a	C	IL3	63 ± 4	64 ± 1
X8C/441C	A	IL4	29 ± 5	28 ± 2
X8C/449C	A	IL4	Inactive	Inactive
X8C/522C^1-a	C	IL5	62 ± 7	55 ± 3
X8C/532C	S	IL5	46 ± 3	71 ± 3
X8C/534C	G	IL5	Inactive	Inactive
X8C/622C^1-a	C	C terminus	33 ± 2	65 ± 11

Transport and binding activities were assayed as described in Materials and Methods. Data are means ± SD from six measurements in three separate experiments expressed as the percentage of transport or binding activity relative to SERT C109A. X8C is SERT with the following substitutions: C15A, C21A, C109A, C147A, C155A, C357I, C522S, and C622A. In constructs such as X8C-357C, one or more of the endogenous cysteine residues was restored in the X8C background. In constructs such as X8C-L137C, an endogenous residue was mutated to cysteine in the X8C background.
↵F1-a Data from Androutsellis-Theotokis et al. (2001).