Purification and functional reconstitution of the 2-oxoglutarate/malate translocator from spinach chloroplasts.

The chloroplast 2-oxoglutarate/malate translocator was solubilized from envelope membranes by the detergent n-dodecyl beta-D-maltoside and purified to apparent homogeneity by anion-exchange chromatography followed by gel permeation chromatography. During the purification procedure, the activity of the translocator was monitored by functional reconstitution into phospholipid vesicles. The purified translocator protein has an apparent molecular mass of about 45,000 as revealed by SDS-PAGE. Based on the specific reconstituted transport activity, the purification was about 31-fold with an overall yield of identical to 50%. The substrate specificity of the purified translocator closely resembles that described for the native transport system in intact chloroplasts.