Effects of EDTA on (Na+-K+) ATPase bound to human erythrocyte membranes]

Membranes preincubation with high EDTA concentration induced an alteration on (Na"-K+) ATPase kinetic behaviour. This effect can be related to a change in calcium content tightly bound to the membranes.     

Solubilization and purification of Na+-K+ ATPase of human erythrocyte mambranes using sodium deoxycholate]

The (Na+-K+)-dependant ATPase prepared from human erythrocyte ghosts has been purified with sodium deoxycholate in a high ionic medium. After the purification, 60% of the native activity bound to the membranes was recovered.     

(Ca−Mg) ATPase activity of human erythrocyte membranes: Influence of incubation buffer

Summary Activity of the (Ca–Mg) ATPase of human red blood cell membranes is highly dependent on the specific buffer used in the ATPase assay. Activity is highest in histidine and/or imidazole buffers and is lowest in HEPES buffer.This research was supported by Public Health Service Grants AH-16436 and GM 00109-16. We wish to acknowledge the useful suggestions of Thomas R. Hinds and the excellent clerical assistance of Ms Laurie Asher.     

Effect of barbiturate on Mg++-dependent ATPase in human erythrocytes

Zusammenfassung Die Aktivität der Mg⁺⁺-abhängigen ATPase in der Membran menschlicher Erythrozyten ändert sich in Anwesenheit von Barbiturat (Barbital der Firma Spofa). 10 mM Barbiturat stimuliert das Enzym, während 100 mM zu einem Verlust der enzymatischen Aktivität führt. Bei Erythrozyten, deren Enzym mit Saponin stimuliert wurde, ist der Einfluss von 10 mM Barbiturat statistisch nicht signifikant. 100 mM Barbiturat hat eine hemmende Wirkung.     

Asymmetrical activation by Ca2+ of the erythrocyte membrane K+-dependent phosphatase

Resumen Los sitios con los cuales se combinan el ion Ca y el ATP para activar la fracción dependiente, ce K⁺ de la fosfatasa de la membrana del glóbulo rojo, están ubicados en la superficie interna de dicha membrana. Esta característica de asimetría, favorece la idea de la relación de esta enzima con la ATPase activada por Ca²⁺ de la membrana del glóbulo rojo.

---

---

This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Argentina, and the Facultad de Farmacia y Bioquímica. A.F.R. and P.J.G. are established investigators from the CONICET.     

The site of action of La3+ in the reaction cycle of the human red cell membrane Ca2+-pump ATPase

Lanthanum (La3+) inhibits the Ca-pump of the red cell by arresting the protein in a phosphorylated form (PI). Similar La3+ concentrations are required to increase the amount of PI and to stop PI-decay. In the presence of La3+ phosphorylation becomes insensitive to Mg2+. PI made in the presence of Mg2+ is not prevented from decaying by subsequent addition of La3+, whereas that made in the absence of Mg2+ is. Taken together, these findings seem to indicate that La3+ blocks the transition between a 1st and a 2nd form of PI.     

Postnatal decline of (Ca2+ + Mg2+)-activated membrane ATPase in cattle red cells.

Acitivity of membrane bound (Ca2+ + Mg2+)-stimulated ATPase, associated with Ca2+ outward transport, in calf red cells is high at birth and declines with a rate constant of 0.041 d-1 after the 3rd week. The decline parallels the disappearance of fetal hemoglobin.     

Effect of cholesterol oxidation on (Na+, K+) ATPase activity of erythrocyte membranes

Summary By incubation of human erythrocyte ghosts with cholesterol oxidase (EC 1.1.3.6) part of the cholesterol of the membrane is replaced by 4-cholesten-3-one. This alteration in the sterol composition is accompanied by an inhibition of the (Na⁺, K⁺) ATPase of the erythrocyte membrane.Acknowledgments. This study was supported by the Deutsche Forschungsgemeinschaft Bonn-Bad Godesberg and the Sonderforschungsbereich 90 of the University of Heidelberg. We thank Mr.J. Schmidt and MissI. Geldmacher for skilful technical assistance.     

Effect of cholesterol oxidation on (Na+, K+) ATPase activity of erythrocyte membranes.

By incubation of human erythrocyte ghosts with cholesterol oxidase (EC 1.1.3.6) part of the cholesterol of the membrane is replaced by 4-cholesten-3-one. This alteration in the sterol composition is accompanied by an inhibition of the (Na+, K+) ATPase of the erythrocyte membrane.     

Temperature acclimation of Mg2+Ca2+-myofibrillar ATPase from a cold-selective teleost,Salvelinus fontinalis: a compromise solution

Summary Brook trout (Salvelinus fontinalis, Mitchill) were acclimated over 15 weeks to either +4°C or +24°C. The effects of temperature on myofibrillar Mg²⁺Ca²⁺-ATPase activities were investigated. In contrast to goldfish, temperature acclimation does not alter the kinetic properties of the brook trout myofibrillar ATPase. Activation energy (G^#) is lower and substrate turnover number is higher than values previously reported for cold-adapted stenotherms. Properties of brook trout ATPase appear to be a compromise enabling function across a broad temperature range. The different strategies of adapting to seasonal temperature variations are briefly discussed.The authors are grateful to the Wellcome Trust for financial support.-Correspondence should be addressed to I.A.J.     

Temperature acclimation of Mg2+Ca2+-myofibrillar ATPase from a cold-selective teleost, Salvelinus fontinalis: a compromise solution

Brook trout (Salvelinus fontinalis, Mitchill) were acclimated over 15 weeks to either +4 degrees C or +24 degrees C. The effects of temperature on myofibrillar Mg2+Ca2+-ATPase activities were investigated. In contrast to goldfish, temperature acclimation does not alter the kinetic properties of the brook trout myofibrillar ATPase. Activation energy (delta G not equal to) is lower and substrate turnover number is higher than values previously reported for cold-adapted stenotherms. Properties of brook trout ATPase appear to be a compromise enabling function across a broad temperature range. The different strategies of adapting to seasonal temperature variations are briefly discussed.     

The influence of the steroid hormones on the physical state of human erythrocyte membranes

Summary Steroids alter the physical state of the regions in the human erythrocyte membrane, where glucose transport is occurring.The work was supported by the Deutsche Forschungsgemeinschaft. We thank Dipl. Phys. P. Geck for the aid in statistical evaluation.