RECONSTITUTION OF LYSOSOMAL SULFATE TRANSPORT IN PROTEOLIPOSOMES

As part of a strategy to purify the lysosomal sulfate transporter, we developed a method for reconstitution of transport in artificial membr ane vesicles. Lysosomal membranes were prepared from Percoll density g radient purified rat liver lysosomes and membrane proteins were solubi lized using the non-ionic detergent, Triton X-100. The solubilized pro teins were mixed with liposomes prepared by sonication of egg yolk lec ithin and the detergent was removed by passage of the mixture over Bio -beads XAD2. The resulting proteoliposomes exhibited saturable sulfate transport with characteristics that were very similar to those observ ed in lysosomal membranes. Transport in proteoliposomes had a K-m of 1 55 mu M, exhibited pH dependence and was sensitive to inhibition by DI DS. Reconstitution of transport in proteoliposomes may be useful as an assay for purification of the lysosomal sulfate carrier.