scholarly journals Calcium binding by human erythrocyte membranes

1971 ◽  
Vol 124 (3) ◽  
pp. 563-571 ◽  
Author(s):  
J. Forstner ◽  
J. F. Manery
Keyword(s):  
Ionic Strength ◽  
Aqueous Phase ◽  
Human Erythrocyte ◽  
Calcium Binding ◽  
Incubation Medium ◽  
Phospholipid Fraction ◽  
Erythrocyte Membranes ◽  
Human Erythrocyte Membranes ◽  
Chloroform Methanol

1. The characteristics of Ca2+ binding to haemoglobin-free human erythrocyte membranes were investigated by using 45Ca and centrifugation partition of ‘ghosts’ from their external incubation medium. Equilibrium of ‘ghosts’ with external Ca2+ required less than 15min. 2. The binding did not vary with temperature in the range 0–37°C. 3. At pH7.4 ‘ghosts’ bound a maximum of 283μmol of Ca2+/g of ‘ghost’ protein, equivalent to 6.85×107 Ca2+ ions per cell. 4. Increasing the ionic strength from 0.01 to 0.46 diminished Ca2+ binding, as did ATP in concentrations ranging from 0 to 15mm in the incubation medium. 5. An increase of the pH from 3.0 to 9.3 caused a marked increase in the amount of Ca2+ bound. 6. Extraction of 45Ca-labelled ‘ghosts’ with chloroform–methanol showed that the distribution of Ca2+ was: 79% protein-bound, 16% lipid-bound, 5% in the aqueous phase, presumably non-bound. Most of the lipid-bound Ca2+ (about 80%) was associated with a phospholipid fraction containing phosphatidylserine, phosphoinositides and phosphatidylethanolamine, giving a molar Ca2+: phosphorus ratio of about 1:2.

scholarly journals Self-digestion of human erythrocyte membranes. Role of adenosine triphosphate and glutathione

1977 ◽  
Vol 164 (2) ◽  
pp. 469-472 ◽  
Author(s):  
A Brovelli ◽  
M Suhail ◽  
G Pallavicini ◽  
F Sinigaglia ◽  
C Balduini
Keyword(s):  
Chemical Composition ◽  
Adenosine Triphosphate ◽  
Human Erythrocyte ◽  
Incubation Medium ◽  
Reduced Glutathione ◽  
Human Erythrocytes ◽  
Erythrocyte Membranes ◽  
Digestion Process ◽  
Human Erythrocyte Membranes

Intact human erythrocytes incubated at 37 degrees C, pH7.4, release a sialoglycopeptide similar in its chemical composition, immunological and aggregation properties to the glycopeptide released by isolated ‘ghost’ membranes. The presence of ATP or reduced glutathione at physiological concentrations in the incubation medium of ‘ghost’ membranes inhibits this self-digestion process.

scholarly journals Solubilization of Native Actin Monomers from Human Erythrocyte Membranes

1986 ◽  
Vol 39 (2) ◽  
pp. 117 ◽  
Author(s):  
Leann Tilley ◽  
Margaret Dwyer ◽  
GB Ralston
Keyword(s):  
Ionic Strength ◽  
Human Erythrocyte ◽  
Dnase I ◽  
Erythrocyte Membranes ◽  
Dnase 1 ◽  
Human Erythrocyte Membranes ◽  
Low Ionic Strength

Up to 50% of the actin in erythrocyte membranes can be solubilized at low ionic strength in a form capable of inhibiting DNAse I, in the presence of 0�4 mM ATP and 0�05 mM calcium. In the absence of calcium and A TP, actin is released but is apparently rapidly denatured. Solubilization of G-actin increases with temperature up to 37�C. At higher temperatures, actin is released rapidly but quickly loses its ability to inhibit DNAse 1.

scholarly journals Interaction of platelet plasma membranes with thrombin-activated platelets

Blood ◽  
1981 ◽  
Vol 57 (2) ◽  
pp. 305-312 ◽  
Author(s):  
HR Prasanna ◽  
HH Edwards ◽  
DR Phillips
Keyword(s):  
Human Erythrocyte ◽  
Plasma Membranes ◽  
Membrane Binding ◽  
Human Platelets ◽  
Platelet Membrane ◽  
Erythrocyte Membranes ◽  
Functional Sites ◽  
Activated Platelets ◽  
Platelet Membranes ◽  
Human Erythrocyte Membranes

Abstract This study described the binding of platelet plasma membranes to either control or thrombin-activated platelets. Glycoproteins in plasma membranes isolated from human platelets were labeled by oxidation with periodate followed by reduction with [3H]NaBH4. Labeled membranes were incubated with either control or thrombin-activated platelets. The amount of membranes bound was measured by separating platelets with bound membranes from solution by rapid centrifugation through 27% sucrose and determining the amount of radioactivity associated with platelets. Five- to sevenfold more membranes bound to thrombin- activated platelets than to control platelets. This enhanced binding of labeled membranes was completely inhibited by an excess of unlabeled platelet membranes. Human erythrocyte membranes had little affinity for either washed or thrombin-activated platelets and therefore did not compete for platelet-membrane binding. Binding of platelet membranes to thrombin-treated platelets was inhibited by prior incubation of the platelets with PGI2 suggesting that the enhanced binding of membranes was to activated platelets. This study demonstrates that the purified platelet membranes have functional sites that can mediate membrane binding to platelets and that quantitation of membrane binding appears to reflect the increased aggregation capability of activated platelets.

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