Glycophorin
Encyclopedia
A Glycophorin is a sialoglycoprotein
Sialoglycoprotein
A sialoglycoprotein is a combination of sialic acid and glycoprotein, which is, itself, a combination of sugar and protein.Glycophorin C is one common sialoglycoprotein....

 of the membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

 of a red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

. It is a membrane-spanning protein and carries sugar molecules. It is heavily glycosylated (60%). Glycophorins are rich in sialic acid, which gives the red cells a very hydrophilic-charged coat. This enables them to circulate without adhering to other cells or vessel walls.

Identification

After separation of red cell membranes by SDS-polyacrylamide gel electrophoresis
SDS-PAGE
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, describes a collection of related techniques widely used in biochemistry, forensics, genetics and molecular biology to separate proteins according to their electrophoretic mobility...

 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
GYPE
Glycophorin-E is a protein that in humans is encoded by the GYPE gene.-Further reading:...

) 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 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
    GYPA
    Glycophorin A , also known as GYPA, is a protein which in humans is encoded by the GYPA gene. GYPA has also recently been designated CD235a .- Function :...

  • Glycophorin B
    GYPB
    Glycophorin B also known as sialoglycoprotein delta and SS-active sialoglycoprotein is a protein which in humans is encoded by the GYPB gene...

  • Glycophorin C
    Glycophorin C
    Glycophorin C plays a functionally important role in maintaining erythrocyte shape and regulating membrane material properties, possibly through its interaction with protein 4.1. Moreover, it has previously been shown that membranes deficient in protein 4.1 exhibit decreased content of glycophorin C...

  • Glycophorin E
    GYPE
    Glycophorin-E is a protein that in humans is encoded by the GYPE gene.-Further reading:...



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

External links

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