Solubilization and partial purification of the Ca2+/Na+ antiporter from the plasma membrane of bovine heart.
Vesicles derived from the plasma membrane of bovine heart muscle catalyze an uptake of 45Ca+ which is dependent on Na+ inside the vesicles and inhibited by external Na+ (Ki = 14 mM). The transporter was solubilized with 2% cholate at high ionic strength (0.5 M NaCl) in the presence of 2.4% soybean phospholipids. Appropriate dilution and sedimentation yielded a preparation of the transporter which could be reconstituted into liposomes. The proteoliposomes catalyzed Ca2+ uptake with a specific activity about 5 times higher than native vesicles. External Na+ inhibited Ca2+ uptake with a Ki of 50 mM. The uptake of Ca2+ was also inhibited when the Na+ gradient was collapsed with nigericin. Ca2+ uptake was stimulated when either valinomycin or dinitrophenol was added to the assay, in line with the known electrogenic nature of the transport system.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D008081:Liposomes; D008565:Membrane Proteins / Q000302:isolation & purification* / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010743:Phospholipids / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*
D002352:Carrier Proteins; D008081:Liposomes; D008565:Membrane Proteins; D010743:Phospholipids; D012964:Sodium; D002118:Calcium