A glycophorin is a

sialoglycoprotein A sialoglycoprotein is a combination of sialic acid and glycoprotein, which is, itself, a combination of sugar and protein. These proteins often contain one or more sialyl oligosaccharides that are covalently bound to the rest of the molecule. ...

of the

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...

of a

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

. It is a membrane-spanning protein and carries sugar molecules. It is heavily glycosylated (60%). Glycophorins are rich in

sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this ...

, which gives the red blood cells a very hydrophilic-charged coat. This enables them to circulate without adhering to other cells or vessel walls. A particular mutation in Glycophorins is thought to produce a 40% reduction in risk of severe malaria.

Identification

After separation of red cell membranes by

SDS-polyacrylamide gel electrophoresis SDS-PAGE (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) is a discontinuous electrophoretic system developed by Ulrich K. Laemmli which is commonly used as a method to separate proteins with molecular masses between 5 and 250 kDa. T ...

and staining with periodic acid-Schiff staining (PAS), four glycophorins have been identified. These have been named glycophorin A, B, C, and D in order of the quantity present in the membrane, gylycophorin A being the most and glycophorin D the least common. A fifth ( glycophorin E) has been identified within the human genome but cannot easily be detected on routine gel staining. In total, the glycophorins constitute ~2% of the total

erythrocyte Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

membrane protein mass. These proteins are also known under different nomenclatures but they are probably best known as the glycophorins.

Family members

The following four human genes encode glycophorin proteins: *

Glycophorin A Glycophorin A (MNS blood group), also known as GYPA, is a protein which in humans is encoded by the ''GYPA'' gene. GYPA has also recently been designated CD235a ( cluster of differentiation 235a). Function Glycophorins A (GYPA; this protein) ...

* Glycophorin B *

Glycophorin C Glycophorin C (GYPC; CD236/CD236R; glycoprotein beta; glycoconnectin; PAS-2) plays a functionally important role in maintaining erythrocyte shape and regulating membrane material properties, possibly through its interaction with protein 4.1. Moreo ...

* Glycophorin E Glycophorin D is now known to be a variant of Glycophorin C.

References

External links

* * Glycoproteins Single-pass transmembrane proteins {{membrane-protein-stub