Distinctive properties of the purified Na-Ca exchanger from rod outer segments.
The Na-Ca exchanger of rod outer segments plays an important role in the regulation of Ca levels in photoreceptor cells. While this transporter shares functional properties with other Na-Ca exchangers, it has several unique features. The purified ROS exchanger migrates as a single band at 220 kDa in SDS-polyacrylamide gels, indicating that the unit size of its polypeptide is larger than other known Na-Ca exchangers (and most transporters). A specific antiserum to the ROS exchanger does not bind to the Na-Ca exchangers found in sarcolemmal vesicles or brain synaptic plasma membranes. Similarly, polyclonal antiserum specific for the cardiac exchanger does not react with ROS or brain proteins. The ROS exchanger requires K for transport activity. By incorporating the purified exchanger into proteoliposomes and measuring the sequestration of K, the actual transport of K is demonstrated. A stoichiometry of 4Na:1Ca,1K for the exchanger of ROS has been measured.
Leser
G P
GP
Visual Sciences Center, University of Chicago, Illinois 60637.
Nicoll
D A
DA
Applebury
M L
ML
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D011188:Potassium; D002118:Calcium