TABLE 1.

Effect of externally added anions on the [¹⁴C]citrate/citrate exchange catalyzed by reconstituted single-Cys site 1 CTP variants

Reconstituted site 1 single-Cys CTP variants were incubated with 1–2 mm [¹⁴C]citrate plus a 25-fold excess of potential competing anion. Controls contained water in place of competing anion. Data are presented as mean percentage inhibition ± S.E. from 3 to 5 experiments. Transport reactions and data calculations were conducted as described under “Experimental Procedures.” Statistical differences among the Cys-less and the site 1 CTP variants with a given anion were evaluated with the one-way analysis of variance test. Significance was then determined with the Bonferroni multiple comparisons post hoc test.

CTP variant	Isocitrate	α-Ketoglutarate	Malate	Succinate	Malonate	Phosphoenolpyruvate	ADP	Phosphate	Pyruvate	Glutamate
Cys-less	60 ± 1	20 ± 2	16 ± 2	18 ± 1	20 ± 6	34 ± 1	17 ± 5	9 ± 2	1 ± 3	−7 ± 9
K83C	50 ± 7	60 ± 1a	62 ± 6a	56 ± 3a	44 ± 3b	60 ± 5a	47 ± 1a	47 ± 7b	3 ± 1	25 ± 9c
R87C	62 ± 5	61 ± 10a	61 ± 4a	53 ± 7a	46 ± 4b	65 ± 3a	43 ± 5b	36 ± 7b	−3 ± 2	22 ± 7c
G119C	57 ± 3	42 ± 8c	32 ± 6	23 ± 4	32 ± 4	51 ± 1b	32 ± 2	29 ± 6	6 ± 6	19 ± 2
R189C	74 ± 2c	78 ± 1a	78 ± 4a	80 ± 2a	68 ± 4a	42 ± 1	29 ± 4	41 ± 4b	52 ± 4a	28 ± 5c

^a p < 0.001 versus Cys-less.

^b p < 0.01 versus Cys-less.

^c p < 0.05 versus Cys-less.