CD235a GYPA (Glycophorin A) [MNS blood group],MN sialoglycoprotein, PAS-2 sialoglycoprotein A
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
Erythrocyte
Red Cell
Erythroid Cell
Stem Cell
Hematopoietic Cell
28 / 28
66 / 66

Expression
CD235a is expressed on hematopoietic stem cells, erythroid cells, red cells and erythrocytes.

Structure
MOLECULAR FAMILY NAME: Belongs to the glycophorin A family.

CD235a is a single-pass type-1 131 aa glycoprotein.  It contains a 72 aa extracellular domain which contains 15 O-glycosylation sites and 1 N-glycosylation site, a 23 aa transmembrane domain which mediates the non-covalent dimerization of the protein not only within the cell membrane and in artificial bilayers in the presence of several detergents and SDS-PAGE conditions and a 36 aa  C-terminal cytoplasmic domain.  CD235a forms α-helical dimers in lipid bilayers.  It contributes to most of the net negative charge on the human erythrocyte membrane which bear the antigenic determinants for the MN and Ss blood groups.  The CD235a gene consists of 7 exons and has a 97% sequence homology with CD235b from the 5'UTR to the coding sequence encoding the 1st 45 aa.  In addition to the M or N and S or s antigens, that commonly occur in all populations, about 40 related variant phenotypes have been identified.  These variants include all the variants of the Miltenberger complex and several isoforms of Sta, and Dantu, Sat, He, Mg, and deletion variants Ena, S-s-U- and Mk.  Most of the variants resulted from the gene recombinations between CD235a and CD235b.

MOLECULAR MASS
Cell Type Unreduced Reduced
36 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION: No information.


Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD235a

CD235a binds CD170, influenza virus and the erythrocyte binding antigen (EBA-175) of Plasmodium falciparum.

Function
CD235a is a major glycoprotein of the erythrocyte cell membrane, of the RBC membrane and is a carrier of the blood group M and N specificities.  Along with CD235b, CD235a is responsible for the MN blood group.  It is thought to prevent cell agglutination.  The N-terminal glycosylated segment, which lies outside the erythrocyte membrane, has MN blood group receptors and also binds influenza virus.  CD235a provides the cell with a large mucin like structure which suggests that this provides a barrier to cell fusion, thereby minimizing aggregation between red cells in the circulation.  CD235a deficiency does not lead to any pathology, possibly this is due to the fact that enhanced glycosylation of other membrane proteins such as band 3.  Association with band 3 in the cell membrane facilitates the membrane expression of the band 3.  Glycosylation can compensate for the absence of the glycophorins or CD235a could be a membrane inhibitor of reactive lysis.  CD235a appears to be restricted to erythroid cells and possibly cells in the kidney cortex.  CD235a is a useful marker to study the developmental biology of hematopietic progenitor cells.  Glycophorin A (GPA) somatic-cell mutation assay is used to assess mutation events at the GPA M/N locus in bone marrow stem cells.  The absence of CD235 in humans is not associated with pathology.  However, the absence of CD235a alters the structure and anion transport properties of CD233.  Anion transport was lower in cells lacking CD235a and optimal surface expression of CD233 requires CD235a and vise versa.
 
BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD235a IN INTACT ANIMAL

It is possible that the diversity of CD235a, in the areas where malaria is endemic, is driven by the evolutionary value of avoiding infection of red cells.  There is evidence that some strains of Plasmodium falciparium binds to CD235a.


Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD235a: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD235a: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 2993P02724
Antibodies
JC159   View Reactivity

Revised June 25, 2008


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