On the red blood cell Ca2+-pump: An estimate of stoichiometry
- 1 December 1978
- journal article
- research article
- Published by Springer Nature in The Journal of Membrane Biology
- Vol. 41 (4), 361-376
- https://doi.org/10.1007/bf01872000
Abstract
Summary Efflux of Ca2+ from reversibly hemolyzed human red blood cell ghosts was determined by a Ca2+ selective electrode, by atomic absorption spectroscopy, and by the use of45Ca. Hydrolysis of ATP was determined by measurement of inorganic phosphate (Pi). At 25°C, ghosts loaded with CaCl2, MgCl2, Na2ATP, and Tris buffer (pH 7.4) extruded Ca2+, with mean rates ranging from 58.8±3.5 (sd) to 74.7±8.2 (sd) μmoles·liter ghosts−1·min− depending on the method of Ca2+ determination. The ratio of Ca2+ transported to Pi released in the presence of ouabain without correction for background ATP splitting was 0.83, 0.83, and 0.80, respectively, for the three methods of Ca2+ determination. Correction for the ATPase activity not associated with Ca2+ transport resulted in a ratio of 0.91:1. In other experiments, the use of La3+ to inhibit the Ca2+-pump allowed an estimate of the ATPase activity associated with Ca2+ extrusion. In the presence of various concentrations of La3+, the ratio of Ca2+ pumped to Pi liberated was 0.86 or 1.02, depending on the method of Ca2+ determination. It is concluded that the stoichiometry of the Ca2+-pump of the RBC plasma membrane is one Ca2+ pumped per ATP hydrolyzed.Keywords
This publication has 19 references indexed in Scilit:
- Transport parameters and stoichiometry of active calcium ion extrusion in intact human red cellsBiochimica et Biophysica Acta (BBA) - Biomembranes, 1977
- The use of ionophores of rapid loading of human red cells with radioactive cations for cation-pump studiesThe Journal of Membrane Biology, 1976
- A rapid and ultrasensitive method to measure Ca++ movements across biological membranesBiochemical and Biophysical Research Communications, 1975
- Calcium transport in human erythrocytesArchives of Biochemistry and Biophysics, 1975
- Determination of the stoichiometry of the calcium pump in human erythrocytes using lanthanum as a selective inhibitorFEBS Letters, 1975
- Studies on a Ca2+-dependent ATPase of human erythrocyte membranes: Effects of Ca2+ and H+Biochimica et Biophysica Acta (BBA) - Biomembranes, 1972
- Studies on the Active Transport of Calcium in Human Red CellsThe Journal of general physiology, 1969
- Active Calcium and Strontium Transport in Human Erythrocyte GhostsThe Journal of general physiology, 1969
- Metabolism of 2,3-diphosphoglycerate and glycolysis in human red blood cells under the influence of dipyridamole and inorganic sulfur compoundsBiochimica et Biophysica Acta (BBA) - General Subjects, 1968
- ATP-dependent Ca++-Extrusion from human red cellsCellular and Molecular Life Sciences, 1966