Erythrocytes membrane skeleton

Bennett, V. (1989). The spectrin-actin junction of erythrocyte membrane skeletons. Biochim. Biophys. Acta 988, 107-121. 

The structure of spectrin and the location of spectrin in the cytoskeleton. (a) An a/3 dimer of spectrin. Both a and f3 subunits are extended structures consisting of end-to-end domains of 106 amino-acyl residues folded into three a helices the subunits twist about one another loosely as shown. (b) The erythrocyte membrane skeleton. Spectrin tetramers ((X2P2), shown in yellow, are linked to the cytoplasmic domain of the anion channel (blue) by the protein ankyrin (red), and to glycophorin and actin filaments by protein 4.1. This structure lends stability to the red cell membrane while maintaining sufficient flexibility to allow erythrocytes to withstand substantial shear forces in the peripheral circulation. 

Model of the organization of the red cell membrane skeleton. [Reproduced, with permission, from S. Lux and S. B. Shohet, The erythrocyte membrane skeleton Biochemistry. Hasp. Prac. 19(10), 82 (1984). R. Margulies, illustrator.]... 

Figure 10.18 Model of the postulated structure of the erythrocyte membrane skeleton. 

Spectrin is a peripheral membrane protein of erythrocytes. It contains two copies each of an ot and a subunit, forming a tetramer. Spectrin acts like a fiber, linking together the various components of the erythrocyte membrane skeleton (Figure 10.18). 

What is the function of the membrane skeleton There is a group of hereditary diseases including spherocytosis in which erythrocytes do not maintain their biconcave disc shape but become spherical or have other abnormal shapes and are extremely fragile.269 272 Causes of spherocytosis include defective formation of spectrin tetramers and defective association of spectrin with ankyrin or the band 4.1 protein.265 273 Thus, the principal functions of these proteins in erythrocytes may be to strengthen the membrane and to preserve the characteristic shape of erythrocytes during their 120-day lifetime in the bloodstream. In other cells the spectrins are able to interact with microtubules, which are absent from erythrocytes, and to microtubule-associated proteins of the cytoskeleton (Chapter 7, Section F).270 In nerve terminals a protein similar to erythrocyte protein 4.1 may be involved in transmitter release.274 The cytoskeleton is also actively involved in transmembrane signaling. 

Bennett, V., The membrane skeleton of human erythrocytes and its implications for more complex cells. Ann. Rev. Biochem. 54 273, 1985. 

The membrane skeleton acts as an elastic semisolid, allowing brief periods of deformation followed by reestablishment of the original cell shape (reviewed by Bennett and Gilligan, 1993). Erythrocytes in the human bloodstream have to squeeze repeatedly through narrow capillaries of diameters smaller than their own dimensions while resisting rupture. A functional erythrocyte membrane is pivotal to maintaining the functional properties of the erythrocyte. This importance is apparent when examination is made of many hemolytic anemias, where mutation of proteins involved in the structure of the submembranous cytoskeleton, and its attachment to the lipid bilayer, result in a malformed or altered cytoskeletal architecture and a disease phenotype. 

All of the proteins just described are examples of integral membrane proteins. As such, they are firmly embedded in the phospholipid bilayer and actually span the membrane one side of the protein faces the cytoplasmic side of the membrane, the other side faces the outer surface of the cell. The erythrocyte membrane also contains a number of peripheral-membrane proteins. Unlike the membrane-spanning integral-membrane proteins, these peripheral-membrane proteins are tightly associated only with the cytoplasmic side of the phospholipid bilayer. Together, these peripheral-membrane proteins form a meshlike matrix or skeleton on the inner surface of the membrane that... 

Tvo additional peripheral membrane proteins anchor the spectrin filaments to the cytoplasmic side of the erythrocyte membrane. One of these polypeptides, the 210-kDa ankyrin protein, binds both a single spectrin molecule and the chloride-bicarbonate anion-exchange protein discussed previously. The second of these polypeptides, actin, is capable of binding several molecules of spectrin. Since actin is able to associate with more than a single spectrin monomer, it acts as a branch point for the spectrin protein as the membrane skeleton or matrix is assembled (see Fig. 13-1). In this experiment, you will determine the concentration of total protein in the erythrocyte membrane through the use of the Folin-Ciocalteau assay. 

Bennett, V. (1985). The Membrane Skeleton of Human Erythrocytes and Its Implications for More Complex Cells. Annu Rev Biochem 54 273. 

PfEMP3, deposited on the cytoplasmic face of the erythrocyte cyto-skeleton, is a component of the electron-dense plaque knob. Although truncation prevented its distribution at the red cell membrane (and knobs... 

The Tx -values for the side chains of DPL in deuterochloroform or sonicated DPL in deuterium oxide buffer were found to increase from the central glycerol moiety toward both the ends of the fatty acid chains and the trimethyl quaternary ammonium group of the choline (Metcalfe et al., 1971). This means that molecular motion becomes more restricted in moving from a methylene further from the glycerol skeleton to one that is closer to this backbone. Additionally, the 13C nmr spectrum of human erythrocyte membranes (10% w/w) in D20 buffer at 28° was also obtained (Metcalfe et al., 1.971). 

Fig. 5. Schematic representation of the architecture of biological membranes, a. Singer and Nicolson concept, proteins are free to move. b. Integral membrane proteins are connected with the membrane skeleton by means of an ankyrin protein, as in the erythrocyte, c. Hormone- or antibody-induced aggregation of receptors resulting in a coated pit. d. Aggregation of proteins in contact sites between cells like the gap junction, e. Paracrystalline protein structures in the plane of the bilayer, as in the purple membrane of Halobacterium halobium. f. Phase separation of lipids resulting in the aggregation of proteins.

Desmosmal and Intermediate junction proteins Erythrocyte membrane and membrane-skeleton Fungal (yeast) plasma membrane Gap junction channel proteins (connexon)... 

Kozlov, M.M. and Markin, V.C. 1986. Membran skeleton of erythrocytes. Theoretical model. Biol. Membr. 

Tuvia, S. Levin, S. Bitler, A. Korenstein, R. Mechanical fluctuations of the membrane-skeleton are dependent on F-Actin ATPase in human erythrocytes. J. Cell Biol. 1998, 141, 1551-1561. 

Principle In this procedure erythrocytes are treated with Triton X-100 which is reported to solubilize the membrane lipid leaving the underlying cytoskeletal network intact. The cyto-skeletons are separated from cytosolic components, Triton and solubilized lipid by centrifugation through a sucrose solution. The high salt concentration of the sucrose solution ensures the removal of residual lipid and integral membrane proteins from the cytoskeletal network. 

Maier, A. G., Rug, M., O Neill, M. T., Beeson, J. G., Marti, M., Reeder, J., and Cowman, A. F. (2007). Skeleton-binding protein 1 functions at the parasitophorous vacuole membrane to traffic PfEMPl to the Plasmodium falciparum-infected erythrocyte surface. Blood 109, 1289-1297. 

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