CD235b GYPB (Glycophorin B) [MNS blood group], PAS-3, sialoglycoprotein δ, ss-active sialoglycoprotein
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
Erythrocyte
Red Cell
20 / 20

Expression
CD235b is expressed on red cells and erythrocytes.

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

CD235b is a single-pass type-1 203 aa glycoprotein.  It contains a 72 aa N-terminal extracellular domain which contains 11 O-linked glycosylation sites, a 22 aa transmembrane domain and a 10 aa C-terminal cytoplasmic domain.  CD235b is believed to facilitate the membrane assembly of the Rh complex.  It contributes to most of the negative charge on the human erythrocyte membrane which bear the antigenic determinants for the MN and Ss blood groups.  The CD235b gene consists of 5 exons and has a 97% sequence homology with CD235a from the 5'UTR to the coding sequence encoding the 1st 45 amino acids.  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 are resulted from the gene recombinations between CD235a and CD235b.

MOLECULAR MASS
Cell Type Unreduced Reduced
20 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION

The N-terminal extracellular domain is heavily glycosylated on serine and threonine residues.

Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD235b: No information.

Function
CD235b is a minor sialoglycoprotein in erythrocytes cell membrane which is a carrier of the blood group S/s.  Along with CD235a, CD235b is responsible for the MN blood group system.  CD235b provides the cell with a large mucin like surface which suggests that this provides a barrier to cell fusion thereby minimizing aggregation between red cells in the circulation.  CD235b 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, can compensate for the absence of the glycophorins or CD235b could appear to be restricted to erythroid cells and possibly cells in the kidney cortex.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD235b IN INTACT ANIMAL: No information.


Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD235b: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD235b: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 2994P06028
Antibodies

Revised June 25, 2008


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