Editing Red blood cell (section)

====Membrane proteins====
[[File:RBC Membrane Proteins SDS-PAGE gel.jpg|thumb|Red blood cell membrane proteins separated by [[Polyacrylamide gel electrophoresis|SDS-PAGE]] and [[Silver staining|silverstained]]<ref>{{cite journal |vauthors=Hempelmann E, Götze O | title =Characterization of membrane proteins by polychromatic silver staining| journal = Hoppe-Seyler's Z Physiol Chem| volume = 365| pages = 241–42| year = 1984 }}</ref>]]
The proteins of the membrane skeleton are responsible for the deformability, flexibility and durability of the red blood cell, enabling it to squeeze through capillaries less than half the diameter of the red blood cell (7–8 μm) and recovering the discoid shape as soon as these cells stop receiving compressive forces, in a similar fashion to an object made of rubber.

There are currently more than 50 known membrane proteins, which can exist in a few hundred up to a million copies per red blood cell. Approximately 25 of these membrane proteins carry the various blood group antigens, such as the A, B and Rh antigens, among many others. These membrane proteins can perform a wide diversity of functions, such as transporting ions and molecules across the red cell membrane, adhesion and interaction with other cells such as endothelial cells, as signaling receptors, as well as other currently unknown functions. The [[blood type]]s of humans are due to variations in surface [[glycoprotein]]s of red blood cells. Disorders of the proteins in these membranes are associated with many disorders, such as [[hereditary spherocytosis]], [[hereditary elliptocytosis]], [[hereditary stomatocytosis]], and [[paroxysmal nocturnal hemoglobinuria]].<ref name="Yazdanbakhsh2000"/><ref name="Mohandas2008"/>

The red blood cell membrane proteins organized according to their function:
[[File:RBC membrane major proteins.png|thumb|Red blood cell membrane major proteins]]
'''Transport'''
* [[Band 3]] – Anion transporter, also an important structural component of the red blood cell membrane, makes up to 25% of the cell membrane surface, each red cell contains approximately one million copies. Defines the [[Diego antigen system|Diego Blood Group]];<ref>{{cite journal | vauthors = Iolascon A, Perrotta S, Stewart GW | title = Red blood cell membrane defects | journal = Reviews in Clinical and Experimental Hematology | volume = 7 | issue = 1 | pages = 22–56 | date = March 2003 | pmid = 14692233 }}</ref>
* [[Aquaporin 1]] – water transporter, defines the [[Colton antigen system|Colton Blood Group]];
* [[Glut1]] – glucose and [[Dehydroascorbic acid|L-dehydroascorbic acid]] transporter;
* [[MCT1]] – [[Monocarboxylate transporter]] for exporting [[Lactic acid]] to the liver. See [[Cori cycle]].;<ref name="pmid29660777">{{cite journal | vauthors = Fisel P, Schaeffeler E, Schwab M | title = Clinical and Functional Relevance of the Monocarboxylate Transporter Family in Disease Pathophysiology and Drug Therapy | journal = Clinical and Translational Science | volume = 11 | issue = 4 | pages = 352–364 | date = July 2018 | pmid = 29660777 | pmc = 6039204 | doi = 10.1111/cts.12551 }}</ref>
* [[Kidd antigen system|Kidd antigen protein]] – urea transporter;
* [[RHAG]] – gas transporter, probably of carbon dioxide, defines Rh Blood Group and the associated unusual blood group phenotype Rh<sub>null</sub>;
* [[Na+/K+-ATPase|Na<sup>+</sup>/K<sup>+</sup> – ATPase]];
* [[Calcium ATPase|Ca<sup>2+</sup> – ATPase]];
* [[Na-K-2Cl cotransporter|Na<sup>+</sup> K<sup>+</sup> 2Cl<sup>−</sup> – cotransporter]];
* [[Sodium-chloride symporter|Na<sup>+</sup>-Cl<sup>−</sup> – cotransporter]];
* [[Na-H exchanger]];
* [[K-Cl cotransporter|K-Cl – cotransporter]];
* [[KCNN4|Gardos Channel]].

'''Cell adhesion'''
* [[ICAM4|ICAM-4]] – interacts with [[integrins]];
* [[Basal cell adhesion molecule|BCAM]]  – a glycoprotein that defines the [[lutheran antigen system|Lutheran blood group]] and also known as [[Lutheran antigen system|Lu]] or [[laminin]]-binding protein.

'''Structural role''' – The following membrane proteins establish linkages with skeletal proteins and may play an important role in regulating cohesion between the lipid bilayer and membrane skeleton, likely enabling the red cell to maintain its favorable membrane surface area by preventing the membrane from collapsing (vesiculating).
* [[Ankyrin]]-based macromolecular complex – proteins linking the bilayer to the membrane skeleton through the interaction of their cytoplasmic domains with [[Ankyrin]].
** [[Band 3]] – also assembles various [[Glycolysis|glycolytic]] enzymes, the presumptive CO<sub>2</sub> transporter, and [[carbonic anhydrase]] into a macromolecular complex termed a "[[metabolon]]," which may play a key role in regulating red cell metabolism and ion and gas transport [[#Role in CO2 transport|function]].
** [[RHAG]] – also involved in transport, defines associated unusual blood group phenotype Rh<sub>mod</sub>.
* [[Band 4.1|Protein 4.1R]]-based macromolecular complex – proteins interacting with [[Band 4.1|Protein 4.1R]].
** [[Band 4.1|Protein 4.1R]] – weak expression of [[Gerbich antigen system|Gerbich]] antigens;
** [[Glycophorin C]] and D – glycoprotein, defines [[Gerbich antigen system|Gerbich Blood Group]];
** [[XK protein|XK]] – defines the Kell Blood Group and the Mcleod unusual phenotype (lack of Kx antigen and greatly reduced expression of Kell antigens);
** [[Rh factor|RhD/RhCE]] – defines Rh Blood Group and the associated unusual blood group phenotype Rh<sub>null</sub>;
** [[Duffy antigen system|Duffy protein]] – has been proposed to be associated with [[chemokine]] clearance;<ref>{{cite journal | vauthors = Denomme GA | title = The structure and function of the molecules that carry human red blood cell and platelet antigens | journal = Transfusion Medicine Reviews | volume = 18 | issue = 3 | pages = 203–231 | date = July 2004 | pmid = 15248170 | doi = 10.1016/j.tmrv.2004.03.006 }}</ref>
** [[ADD1|Adducin]] – interaction with band 3;
** [[EPB49|Dematin]]- interaction with the Glut1 glucose transporter.
<ref name="Yazdanbakhsh2000"/><ref name="Mohandas2008"/>