title: Isolation, purification, and reconstitution of a proline carrier protein from Mycobacterium phlei.
abstract: Membrane vesicles from Mycobacterium phlei contain carrier proteins for proline, glutamine, and glutamic acid. The transport of proline is Na+ dependent and required substrate oxidation. A proline carrier protein was solubilized from the membrane vesicles by treatment with cholate and Triton X-100. Electron microscopic observation of the detergent-treated membrane vesicles showed that they are closed structures. The detergent-extracted proteins were purified by means of sucrose density gradient centrifugation, followed by gel filtration and isoelectric focusing. A single protein with a molecular weight of 20,000 +/- 1000 was found on polyacrylamide gel electrophoresis. Reconstitution of proline transport was demonstrated when the purified protein was incubated with the detergent-extracted membrane vesicles. This reconstituted transport system was specific for proline and required substrate oxidation and Na+. The purified protein was also incorporated into liposomes, and proline uptake was demonstrated when energy was supplied as a membrane potential introduced by K+ diffusion via valinomycin. The uptake of proline was Na+ dependent and was inhibited by uncoupler or by sulfhydryl reagents.
mesh_terms: D001692:Biological Transport; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D009161:Mycobacterium / Q000378:metabolism*; D009168:Mycobacterium phlei / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D011510:Proteolipids / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008081:Liposomes; D011510:Proteolipids; D011392:Proline