Reconstitution into liposomes of the Na+-dependent transport systems for cyclacillin,an aminopenicillin,from brush border membranes of rat small intestine

Triton X-100 extract from brush border membranes of rat small intestine was recombined with egg phosphatidylcholine liposomes by the freeze-thaw sonication method. The treated liposomes showed a Na⁺-dependent uptake of cyclacillin, which was inhibited by a low concentration of mercuric ions and L-phenylalanylglycine, but not by glycine. These are consistent with the absorption characteristics of the antibiotic in situ and indicate that reconstitution of the Na⁺-dependent active cyclacillin transport system of rat small intestine has been achieved.