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PubMed2000

Mechanism of selective release of membrane proteins from human erythrocytes in the presence of liposomes.

Incubation of erythrocytes with liposomes results in the release of shed vesicles rich in glycosyl-phosphatidylinositol (GPI)-anchored proteins but poor in transmembranous proteins. We investigated the mechanisms of membrane protein polarization by examining the effect of the interaction between spectrin and membrane proteins on the release of a transmembranous protein, band 3, and a GPI-anchored protein, acetylcholinesterase (AChE), from erythrocyte ghosts. Polymerization of spectrin resulted in a 30-fold decrease in the released amount of band 3 per constant amount of shed vesicles but did not affect the amount of released AChE per constant amount of shed vesicles. On the other hand, the amount of released band 3 per constant amount of shed vesicles increased by cleaving the cytoplasmic part of band 3. Our results first demonstrated that the diffusibility of membrane proteins determined by steric hindrance between membrane proteins and protein mesh primarily determines the ease of localization of membrane proteins into shed vesicles. Taken together with the recent biophysical studies, we built a "fence selection model" that retrograding spectrin mesh sweeps diffusing band 3 molecules from the tip of the membrane crenated area toward the entry of the crenated area, but not AChE molecules. Our study describes a novel method for isolation of a large number of vesicles containing special and intact membrane proteins from cells not by using detergents or organic solvents, but by utilizing the fence effect between the cytoskeleton and membrane proteins.

Acetylcholinesterase↗
PubMed1995

Functional link between phosphorylation state of membrane proteins and morphological changes of human erythrocytes.

The Tyr-phosphorylation of the cytoplasmic domain of the major membrane-spanning band 3, rather than the Ser/Thr-phosphorylation of the membrane proteins (spectrin and band 3 itself), might be functionally related to certain morphological changes of human erythrocytes. This view is supported by the following lines of evidence: a) vanadate or its derivative pervanadate (vanadyl hydroperoxide), which markedly increase the Tyr-phosphorylation of band 3 (without practically affecting the Ser/Thr-phosphorylation of spectrin) promotes a crenation of human erythrocytes; b) okadaic acid, which selectively increases the Ser/Thr-phosphorylation of spectrin and other membrane proteins, does not promote any shape change, at least at a level detectable with scanning electron microscopy.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2001

Interaction of syntaxin with alpha-fodrin, a major component of the submembranous cytoskeleton.

The soluble N-ethyl maleimide-sensitive factor attachment protein receptor machinery is involved in membrane docking and fusion. In this machinery, the syntaxin family is a central coordinator and participates in multiple protein-protein interactions. In this study we have shown that alpha-fodrin, nonerythroid spectrin, is a new binding partner of the syntaxin family. alpha-Fodrin bound to syntaxin-1a, -3, and -4, all of which are localized on the plasma membrane. Syntaxin-3 interacted with alpha-fodrin in dose-dependent and saturable manners but not with alpha-spectrin, erythroid spectrin. Syntaxin-3 interacted with alpha-fodrin through its C-terminal coiled-coil region. Binding of Munc18 or SNAP-25 to syntaxin-1a inhibited the interaction of alpha-fodrin with syntaxin-1a. Available evidence indicates that alpha-fodrin is implicated in exocytosis, but a precise mode of action of alpha-fodrin in exocytosis remains unclear. Our results suggest that alpha-fodrin regulates exocytosis through the interaction with members of the syntaxin family.

Animals↗
PubMed2002

Effects of Nf2 missense mutations on schwannomin interactions.

Most benign brain tumors are associated with loss of the Nf2 gene tumor suppressor product schwannomin/merlin. Interactions between schwannomin fragments have given rise to hypotheses of in vivo schwannomin folding and dimerization. Previously, we showed that schwannomin with missense mutations L360P, L535P, and Q538P alters interaction with betaII-spectrin and Hrs. Using yeast two-hybrid tests of interaction, we now show the effects of 11 Nf2 missense mutations on schwannomin self-interaction as well as schwannomin interaction with Hrs isoforms 1 and 2, betaII-spectrin, and p110. Missense mutations L46R and K364I significantly decreased affinity of schwannomin for binding all interacting proteins. The schwannomin L46R mutation may result in a complex conformational change that alters folding and denies betaII-spectrin access to an intact binding site in the C-terminal half of schwannomin. We show that unique inter- and intramolecular interactions occur for schwannomin isoform 2, suggesting that this schwannomin isoform has unique functional properties compared to schwannomin isoform 1.

Brain Neoplasms↗
PubMed1995

Effect of antibodies to membrane skeletal proteins on the shape of erythrocytes and their ability to respond to shape-modulating agents. Important role of 4.1 protein in the determination/maintenance of the discoid shape of erythrocytes.

Monospecific anti-spectrin, anti-4.1 protein, anti-ankyrin, and anti-band 3 cytoplasmic domain antibodies were individually internalized in human erythrocytes by hypotonic lysis in the presence of 2 mM Mg-ATP. The concentrations of the polyclonal antibodies, or their Fab fragments, varied from 0.5 to 4.0 mg/ml. After resealing and glutaraldehyde fixation, the shape of the erythrocytes was examined by phase-contrast or scanning electron microscopy. The antibody-internalized cells were also treated, prior to fixation, with dinitrophenol, chlorpromazine (membrane-penetrable crenation- and cup-forming agents, respectively), or serum albumin (membrane nonpenetrating cup-forming agent). Anti-spectrin antibodies produced a cup shape in the cells at low concentrations (0.5 mg/ml), with a few cells showing multiple cavities. The proportion of the latter increased with increasing concentration of the antibody. The Fab fragments of the antibody were without any effect on the shape. At lower concentrations of anti-4.1 antibodies (0.5 and 1 mg/ml), crenations were observed in antibody-internalized cells. At higher antibody concentrations, the cells underwent sphering. These looked dense under the phase-contrast microscope and often were found to project vesicles from their surface via long stalks. These were generally absent on cells when viewed under the electron microscope, probably due to their breakage during processing. The Fab fragments of the anti-4.1, at equimolar concentrations, were as effective as the intact antibody in altering the cell shape. Anti-ankyrin antibodies or the Fab fragments produced no effect on the shape of the cell. The intact anti-band 3 cytoplasmic domain antibodies, but not their Fab fragments, produced cups at low concentrations and multiple cavities at higher concentrations and multiple cavities at higher concentrations. The anti-spectrin- and anti-band 3 cytoplasmic domain-internalized cells resisted the shape-modulating actions of dinitrophenol, chlorpromazine, and serum albumin. The anti-4.1 antibody-internalized cells also did not respond to dinitrophenol and serum albumin; however, they were converted to contracted cups in the presence of high concentration of chlorpromazine. The cells in which anti-ankyrin antibodies were internalized responded to the actions of the shape-changing agents similarly to normal cells. The results show that the 4.1 protein plays an important role in the determination or maintenance of the normal shape of the erythrocyte and that the cells possessing antibody-modified membrane skeleton do not respond to amphiphilic ions in the manner that normal cells do.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1999

Initiating mechanisms involved in the pathobiology of traumatically induced axonal injury and interventions targeted at blunting their progression.

To gain better insight into the initiating factors involved in traumatically induced axonal injury cats and rats were subjected to various forms of traumatic brain injury. Following injury at intervals ranging from 10 min. to 3 hours, the animals were sacrificed and prepared in accordance with multiple immunocytochemical strategies capable of detecting focal changes in the axolemma, the subaxolemmal spectrin network, the underlying cytoskeleton as well as any related abnormalities in axoplasmic transport. Through these approaches it was recognized that the most severe forms of injury resulted in focal abnormalities of axonal permeability which were observed together with calpain-mediated spectrin proteolysis in the subaxolemmal network. These events were associated with compaction of the underlying neurofilaments and some microtubular loss which occurred without any direct evidence of overt axoplasmic proteolysis with the exception of the most severely injured fibers. In addition to these severely injured axonal profiles, other injured axons did not manifest overt changes in axolemmal permeability or early calpain-mediated spectrin proteolysis but demonstrated dramatic neurofilament and microtubular misalignment and impaired axoplasmic transport. Lastly, other small caliber axons showed another form of intraaxonal change manifested in the local pooling of organelles in the nodal and paranodal regions, with the suggestion that some of these changes may be reversible. In relation to these axonal responses the efficacy of various therapeutic investigations were assessed. The use of calcium chelators showed a trend for protection in those axons manifesting altered axolemmal permeability. However, the use of early and delayed hypothermia demonstrated dramatic protection resulting in significant reduction in the number of damaged axonal profiles. These studies illustrate the diversity and complexity of those axonal responses evoked by traumatic brain injury, suggesting that multiple forms of therapy may be needed to blunt these multifaceted forms of progression.

Animals↗
PubMed1987

The cytoskeleton of isolated murine primitive erythrocytes.

Cytoskeletons of primitive erythrocytes have been isolated from the embryos of day 12 pregnant C57/Bl mice and examined by transmission electron microscopy, immunofluorescence microscopy, and SDS-polyacrylamide gel electrophoresis. Microtubules are the most prominent cytoskeletal component. They are found either singly or organized into loose bundles just under the plasma membrane, but do not form classical marginal bands in most cells. Immunofluorescence with a polyclonal tubulin antiserum confirms this distribution and further reveals numerous mitotic figures among cells. Rhodamine-conjugated phalloidin and heavy meromyosin labeling reveal that actin is localized in the cortex of the primitive erythrocyte in the form of 6 nm filaments. Antibody directed against avian erythrocyte alpha spectrin demonstrates that spectrin is also found in the cortex. Occasional 10-nm intermediate filaments, observed in the primitive erythrocytes by electron microscopy, are believed to be of the vimentin class based on positive reaction of the cells with vimentin-specific antiserum. In addition, a band in erythrocyte cytoskeletons comigrates in SDS-polyacrylamide gels with vimentin isolated from mouse kidney. Spectrin and actin were also found to be associated with the membrane of primitive erythrocytes when membrane ghost preparations were analyzed by SDS-polyacrylamide gel electrophoresis.

Actin Cytoskeleton↗
PubMed1990

Effect of magnesium ions on red cell membrane properties.

Spectrin forms aggregates in solution when incubated at relatively high concentrations (several millimolar) of divalent cations. According to the evidence of electron microscopy, aggregates of globular appearance and rather uniform size are cooperatively formed from spectrin dimers, no intermediate structures being seen. Inter-dimer chemical cross-linking of spectrin in intact red cell membranes is enhanced if magnesium ions at a concentration of 0.5 mM or more are present. On the other hand, the elimination of magnesium from the interior of intact cells causes no significant change in shear elastic modulus, measured by micropipette assays, nor is there any dependence of membrane filtration rate on intracellular free magnesium concentration in the range 0-1 mM. Magnesium-depleted cells are, however, converted into echinocytes within a short period, in which control cells, exposed to ionophore and external magnesium ions, remain completely discoid. Magnesium-depleted cells also undergo structural changes on heating below the temperature at which vesiculation sets in. These reveal themselves by the transformation of the cells to a unique characteristic shape, by grossly reduced filtrability, and by extensive agglutination of the cells when treated with a bifunctional reagent. Magnesium ions thus regulate the stability, but not to any measurable extent the gross elasticity, of the red cell membrane.

Cross-Linking Reagents↗
PubMed1993

Transgenic and mutant animal models to study mechanisms of protection of red cell genetic defects against malaria.

Malaria, caused by members of the genus Plasmodia, is still the most prevalent parasitic disease in the world. In an attempt to understand genetic factors conferring resistance to malaria, mouse models of thalassemia, sickle trait, and ankyrin and spectrin deficiency were studied during infection with species of malaria infectious to rodents. Although growth of P. falciparum is not inhibited in thalassemic erythrocytes in culture, mice carrying a beta-thalassemia mutation were protected from Plasmodium chabaudi adami, supporting epidemiologic findings. Transgenic mice expressing beta s hemoglobin were also significantly protected from two species of rodent malaria. Importantly, a significant role for the spleen in protection in the beta s transgenic mice was found. Finally, mice deficient in spectrin and ankyrin were studied with respect to their ability to support the growth of malaria. It was found that spectrin deficient mice were almost completely refractory to P. chabaudi adami and P. berghei. These models will allow further study of host factors in resistance to malaria.

Animals↗
PubMed1981

A circular dichroism study of human erythrocyte ghost proteins during exposure to 2450 MHz microwave radiation.

The effect of 2450 MHz microwave radiation on the proteins of human erythrocyte ghosts has been investigated using circular dichroism spectroscopy. A specially constructed waveguide inserted into the spectropolarimeter allowed the continuous recording of optical activity before, during and after microwave irradiation. The data indicate that high levels of microwave radiation (600 mW/g, specific absorption rate) induce decreases in alpha-helical conformation that may result from both thermal vibrations and increased strain on the intramolecular hydrogen bonds that maintain secondary structure. The latter effect may result from differential intramolecular interactions with the oscillating electric field. Spectrin (bands 1 and 2) isolated from the ghosts was more sensitive to microwave irradiation than intact ghosts, and spectrin-depleted vesicles were the least sensitive. The data, therefore, indicate that the alpha-helical conformation of spectrin is altered by high levels of microwave radiation.

Circular Dichroism↗
PubMed1997

Reduced sarcolemmal dystrophin distribution and upregulation of utrophin in the cardiac and skeletal muscles of CHF-146 dystrophic hamsters.

Abnormalities in the dystrophic gene product, dystrophin, have been implicated in initiating the primary membrane defect and excessive intracellular calcium accumulation (EICA), which play fundamental pathogenic roles in hereditary muscular dystrophy (HMD). Two other cytoskeletal proteins, spectrin and utrophin, bear remarkable structural and functional homologies to dystrophin. CHF-146 strain dystrophic hamsters (DH), like patients with Duchenne muscular dystrophy (DMD), die prematurely from cardiopulmonary insufficiency, focal myonecrosis, and progressive degeneration of the cardiac and skeletal muscles with EICA. Although DH present a suitable model for HMD, there are controversies concerning their dystrophin and utrophin status. Using immunocytochemistry and Western blotting, we studied dystrophin, spectrin and utrophin anomalies in the cardiac and skeletal muscles of 6-mo-old male DH. Age- and sex-matched CHF-148 strain albino normal hamsters (NH) served as controls. Sarcolemmal dystrophin staining was much weaker and interruptive in the DH. The densitometric analysis of the immunoblots revealed that dystrophin is reduced in DH by 83% in cardiac muscle (p < 0.0001), and by 50% in skeletal muscle (p < 0.0001). We conclude that sarcolemmal dystrophin distribution is markedly reduced and discontinuous in the cardiac and skeletal muscles of DH, with simultaneous upregulation of utrophin and a varied degree of spectrin labelling. This observation suggests that reduced sarcolemmal dystrophin is associated with membrane hyperpermeability, which leads to progressive muscle degeneration via EICA and segmental necrosis in DH. As in DMD, utrophin appears to play an important compensatory role in hamster dystrophinopathy.

Animals↗
PubMed2000

Adducin: structure, function and regulation.

Adducin is a ubiquitously expressed membrane-skeletal protein localized at spectrin-actin junctions that binds calmodulin and is an in vivo substrate for protein kinase C (PKC) and Rho-associated kinase. Adducin is a tetramer comprised of either alpha/beta or alpha/gamma heterodimers. Adducin subunits are related in sequence and all contain an N-terminal globular head domain, a neck domain and a C-terminal protease-sensitive tail domain. The tail domains of all adducin subunits end with a highly conserved 22-residue myristoylated alanine-rich C kinase substrate (MARCKS)-related domain that has homology to MARCKS protein. Adducin caps the fast-growing ends of actin filaments and also preferentially recruits spectrin to the ends of filaments. Both the neck and the MARCKS-related domains are required for these activities. The neck domain self-associates to form oligomers. The MARCKS-related domain binds calmodulin and contains the major phosphorylation site for PKC. Calmodulin, gelsolin and phosphorylation by the kinase inhibit in vitro activities of adducin involving actin and spectrin. Recent observations suggest a role for adducin in cell motility, and as a target for regulation by Rho-dependent and Ca2+-dependent pathways. Prominent physiological sites of regulation of adducin include dendritic spines of hippocampal neurons, platelets and growth cones of axons.

Actins↗
PubMed1980

The formation of vesicles retaining sodium-dependent transport systems for amino acids from protein-depleted membranes of pigeon erythrocytes.

The process of the formation of vesicles from pigeon erythrocyte membranes was studied. Mildly alkaline solutions of low ionic strength, which reduce human erythrocyte membranes to small vesicles depleted of spectrin and other proteins, have no such effect on pigeon erythrocyte ghosts. A distinct phase of removal of membrane proteins, including spectrin, began to occur only when pigeon erythrocyte membranes were exposed to 0.2 mM EDTA adjusted to pH values above 10.2. Vesicles which demonstrated Na+-dependent amino acid transport were generated between the pH values 10.8 and 11.4. The results show that peripheral proteins, notably spectrin, maintain the integrity of the pigeon erythrocyte ghost. The interaction of these proteins with the membrane is rather different from that well studied in the human erythrocyte ghost and the possible significance of this for the pigeon erythrocyte is discussed.

Alanine↗
PubMed1983

Tetracaine modifies the fragmentation mode of heated human erythrocytes and can induce heated cell fusion.

It is known that human erythrocytes in saline fragment by development of an unstable surface wave on the cell rim when cells are heated through the denaturation temperature of the structural protein, spectrin. Here the influence of tetracaine on the fragmentation process has been recorded and analysed by video microscopy of cells heated in rectangular glass microcapillaries. The number of waves per cell rim decreases with increasing tetracaine concentration until, at 0.5 mM tetracaine, wave growth on the cell rim is suppressed on most cells and the cells internalize membrane at the cell dimple. The rate constant for the change in the number of waves per cell with increasing tetracaine concentration is 9.6 mM-1 at a heating rate of 0.5 K/s. 50% of heated cells internalize membrane at 0.14 mM tetracaine. When cells are heated rapidly in suspension in test tubes the presence of tetracaine reduces the temperature for 50% haemolysis from 66 degrees C for washed control cells to 60.5 degrees C for cells in 2 mMs tetracaine. Cells heat in microcapillaries in tetracaine concentrations of 3 mM and higher begin to swell before the spectrin denaturation temperature is reached. Cell fusion was observed at and above the spectrin denaturation temperature in cells heated in 3 and 4 mM tetracaine. It was also noted that the morphology of erythrocytes maintained in 3.6 mM tetracaine for times up to 30 min at 37 degrees C or 20 degrees C was strongly dependent on temperature and time.

Cell Fusion↗
PubMed1987

p-Chloromercuribenzoate-induced dissociation of cytoskeletal proteins in red blood cells of rats.

Effects of p-chloromercuribenzoate (PCMB) on the cytoskeletal organization of rat red blood cells were studied. Upon incubation with 50 microM PCMB in 10 mM Tris-HCl (pH 7.4) at 37 degrees C for 30 min, 80% of actin and 45% of spectrin were released from the ghosts, resulting in the fragmentation of ghost membranes. Addition of 2 mM Mg2+ or 0.1 M KCl, or lowering incubation temperature to 0 degree C substantially inhibited the solubilization of the cytoskeletal proteins and the fragmentation of ghost membranes, which enable to examine the effects of PCMB on the interaction between transmembrane proteins and the peripheral cytoskeletal network. Decreased recoveries of transmembrane proteins, such as band 3 and glycophorin, in Triton shell fraction were observed in the ghosts incubated with PCMB either in the presence of Mg2+ or at 0 degree C. PCMB also inhibited the in vitro association of purified spectrin with spectrin-depleted inside-out vesicles through interaction with proteins in the vesicle, such as bands 2.1 and 3. In the PCMB-treated ghosts, intramembrane particles were highly aggregated, which further supports the PCMB-induced dissociation of the transmembrane proteins from the cytoskeletal network. The decreased recovery of glycophorin in the Triton shell fraction also observed in intact red blood cells upon incubation with PCMB. These results suggest that the main action of PCMB on red cell membranes under physiological condition, at higher ionic strength and in the presence of Mg2+, is to dissociate transmembrane proteins from the peripheral cytoskeletal network, which may modify functions of these proteins.

Actins↗
PubMed1988

Abnormal erythrocyte membrane cytoskeleton structure in chronic myelogenous leukaemia.

Chronic myelogenous leukaemia (CML) is a haematologic malignancy characterised by excessive growth of myeloid cells and their progenitors. Our studies show that there are several abnormalities in CML red blood cells. The proportion of spectrin dimers compared to tetramers extracted from membranes at 4 degrees C, under low ionic strength conditions, increased in CML erythrocytes. These also displayed abnormal thermal sensitivity (between 45 and 46 instead of 49 degrees C). Decreased spectrin tetramer formation observed in several hereditary anaemias has been associated with decreased red cell deformability leading to splenic sequestration. This could also be one of the causes of the severe anaemia observed in CML. Crosslinking with the bifunctional reagent, dimethyl adipimidate (8.6 A) showed significant organizational modification of not only spectrin, but other cytoskeletal components such as ankyrin, bands 4.2 and 5. Enhanced concanavalin A agglutinability of CML erythrocytes also suggests altered topographic distribution of a functionally important membrane protein, band 3.

Concanavalin A↗
PubMed1990

The dissociation of peripheral proteins from erythrocyte membranes brought about by p-mercuribenzenesulfonate.

The organic mercurial p-mercuribenzenesulfonate in 5 mM phosphate buffer (pH 8.0) solubilized ankyrin, bands 4.1 and 4.2, and glyceraldehyde-3-phosphate dehydrogenase from spectrin-depleted erythrocyte membranes. Glyceraldehyde-3-phosphate dehydrogenase was the protein most readily solubilized, being almost completely extracted by 0.5 mM reagent. The solubilization of ankyrin was similar to that of band 4.2, both showing maximal solubilization with 1.0 mM reagent. Band 4.1 was not appreciably solubilized below 2.5 mM p-mercuribenzenesulfonate. N-Ethylmaleimide did not itself solubilize proteins from ghosts or spectrin-depleted vesicles, and pretreatment at low temperature by 4 mM N-ethylmaleimide did not prevent subsequent solubilization by the mercurial. However, pretreatment at 37 degrees C with N-ethylmaleimide inhibited subsequent solubilization of ankyrin and band 4.2 by the mercurial and also resulted in the loss of binding of 1 mol mercurial per mol band 3. These data suggest that release of ankyrin and band 4.2 from the membrane by mercurial is linked to modification of band 3 by the reagent. After incubation of intact erythrocyte membranes with 0.1 M NaCl, treatment with p-mercuribenzenesulfonate selectively solubilized actin from the membranes. The resulting actin-depleted membranes did not vesiculate, but became spherical and lost their biconcave shape. Fragmentation was observed after subsequent removal of spectrin at low ionic strength.

Blood Proteins↗
PubMed1993

Alteration of the erythrocyte membrane via enzymatic degradation of ankyrin (band 2.1): subcellular surgery characterized by EPR spectroscopy.

A fraction of band 3 protein, the major transmembrane protein of erythrocyte membranes, is held to the cytoskeletal protein spectrin via noncovalent interactions with the protein ankyrin (band 2.1). In this study, trypsin was used under defined conditions to selectively proteolyze ankyrin and thereby destroy the band 3-ankyrin linkage on the cytoplasmic side of erythrocyte ghost membranes. Electron paramagnetic resonance (EPR) spectroscopy, in conjunction with selective spin labeling methods, was used to monitor conformational changes occurring in cytoskeletal proteins or cell-surface carbohydrates as a result of this treatment. Treatment of RBC ghosts with TPCK-trypsin for 5 s at 0 degrees C caused an approx. 56% increase in the relevant EPR parameter of a maleimide spin label bound to spectrin (P < 0.004), indicative of increased segmental motion of the spin label and decreased protein-protein interactions. Analysis of the apparent rotational correlation time parameter tau of a spin label covalently and selectively bound to terminal sialic acid residues of glycophorin showed no significant effect from trypsin treatment. However, tau of spin label covalently and specifically bound to terminal galactose residues of cell-surface glycoconjugates of band 3 and other transmembrane glycoproteins significantly decreased with tryptic uncoupling of the ankyrin linkage (P < 0.005). These results suggest a marked conformational alteration in both cytoskeletal and transmembrane proteins as a result of uncoupling from ankyrin. Spermine (N,N'-bis(3-aminopropyl)tetramethylenediamine), a naturally occurring polyamine known to strengthen cytoskeletal protein-protein interactions (Wyse and Butterfield (1988) Biochim. Biophys. Acta 941, 141-149), was used to partially reverse the trypsin-induced cytoskeletal alterations. Addition of 2 mM spermine to ghosts previously treated with trypsin increased cytoskeletal protein-protein interactions as indicated by EPR (P < 0.002). SDS-PAGE was used to confirm the integrity of spectrin, band 3, and band 4.1 in all experiments. The results are discussed with reference to transmembrane signaling mechanisms and membrane-associated pathologies.

Anion Exchange Protein 1, Erythrocyte↗