Table I. Dependence on internal substrate of the transport properties of proteoliposomes reconstituted with recombinant citrin, aralar1 or their C-terminal domains (CTDs).

Internal substrate	Substrate transport (µmol/min/g protein)
	Citrin		Citrin CTD	Aralar1		Aralar1 CTD
	[14C]Aspartate	[14C]Glutamate	[14C]Aspartate	[14C]Aspartate	[14C]Glutamate	[14C]Aspartate
None (Cl– present)	1.4	1.3	1.6	0.3	0.3	0.3
l-Aspartate	92.8	72.5	178.4	25.2	17.1	40.5
l-Glutamate	55.3	90.3	118.1	16.1	21.8	23.7
l-Cysteinesulfinate	81.2	65.9	133.8	17.7	14.2	27.6
l-Aminoadipate	4.6	6.4	6.7	1.6	1.2	2.4
d-Aspartate	8.1	8.9	13.4	1.5	1.9	3.4
d-Glutamate	5.9	9.7	11.3	1.6	2.3	4.1
l-Asparagine	10.1	10.5	18.6	3.1	2.5	5.7
l-Glutamine	1.5	4.7	2.3	0.7	1.3	1.3
l-Cysteate	12.9	11.2	25.5	3.1	3.2	5.5
l-Homocysteinesulfinate	1.1	2.1	2.7	0.2	0.1	0.3
l-Homocysteate	1.8	2.0	4.5	0.1	0.3	0.9

Proteoliposomes were pre-loaded internally with various substrates (concentration, 20 mM). Transport was started by the external addition of 50 µM [¹⁴C]aspartate or 200 µM [¹⁴C]glutamate and terminated after 30 s (citrin and its CTD) or 1 min (aralar1 and its CTD). Similar results were obtained in at least three independent experiments for each carrier investigated.