ISSN:
0091-7419
Keywords:
human erythrocytes
;
ATP-dependent Ca uptake
;
(Ca+Mg)-ATPase
;
spectrin
;
inside-out vesicles
;
Life Sciences
;
Molecular Cell Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Ghost membranes prepared from human erythrocytes exhibit 2 distinct (Ca+Mg)-ATPase1 activities (Quist and Roufogalis, Arch Biochem Biophys 168:240, 1975). (Ca+Mg)-ATPase activity dependent on a water soluble protein fraction is selectively lost from ghost membranes during preparation of vesicles under low ionic strength, slightly alkaline conditions. In this study, the Ca2+ dependence of the remaining membrane bound (Ca+Mg)-ATPase activity and ATP-dependent Ca uptake in vesicles were compared. The C2+ activation curves for (Ca+Mg)-ATPase activity and Ca uptake into vesicles were parallel over a Ca2+ range of 0.3-330 μM, and both curves have 2 apparent KA values for Ca2+ of 0.45 and 100 μM. Addition of a concentrated soluble protein fraction containing predomintly spectrin to the vesicles increased (Ca+Mg)-ATPase activity over twofold but did not affect the rate of Ca uptake. These findings suggest that the (Ca+Mg)-ATPase activity remaining in vesicles after extraction of the water soluble proteins is associated with the Ca pump whereas (Ca+Mg)-ATPase activity dependent on the soluble protein fraction is associated with some other function.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jss.400060310
