FIGURE 4.

Ability of various internal anions to support the influx of external [¹⁴C]citrate with the Cys-less control CTP and binding site 1 CTP variants. Time courses of [¹⁴C]citrate uptake into liposomes reconstituted with CTP variants are presented. The proteoliposomes were reconstituted with 50 mm anionic substrate and the exchange was triggered by addition of 2 mm [¹⁴C]citrate. The internal anions included are defined in the inset within a given panel. Data points are presented as means ± S.E. Transport reactions were conducted as described under “Experimental Procedures.”