CD44 has molecular weight of around 84kDa. Its variant has usually a higher molecular weight. Conversion of 1-742 amino acid of CD44 mRNA gives the mass of 84kDa. This full length includes the variants exon (if I am correct). Since the variants region are not encoded in CD44, but only in CD44v, how does the CD44 have a molecular weight of 84kDa? How can the CD44v have mass that is more than 84kDa? Does the glycosylation and other modification account for the CD44v mass more than 84kDa?
Dear Amit; this review does not answer directly what you are asking, but you can get some idea in molecular structures of standard and spliced variant CD44.
I'm quite sure that the variant exons are not expressed in the standard CD44. The CD44 gene has 18 exons, 9 of which are expressed in the standard protein. The 9 variant exons (v2-v10) are located between exon 5 and 6 of the standard CD44. A CD44 variant will express the 9 standard exons plus a variant exon, which would make it have a higher mass than the standard CD44.
Thank you Pawel Buczkowicz. I also think so, but how CD44 has the molecular size of about 84kDa? Since all amino acids of full length CD44 mRNA are not expressed in CD44, CD44 is supposed to have mass less than 84kDa? Does the glycosylation and other post transcriptional modification accounts for the increased size?
the variant exons are quite small. and don't forget that all all of the variant exons are expressed (this depends on the type of cell, for example). So, CD44 and CD44 should have a very similar size, that is not possible to resolve in a gel. Besides, CD44 variants are way less expressed than the "standard" CD44 (at least in the cell lines im working with)
Yes, glycosylation can account for the increased size of the protein. Many proteins can present more than half of their molecular weight in glycan structures attached to the protein backbone. You can search in NetOglyc and NetNglyc to see if the CD44 have potential glycosylation sites, just to have an idea if this could be happening.
Dear Amit; this review does not answer directly what you are asking, but you can get some idea in molecular structures of standard and spliced variant CD44.
Hi Uede,
Is Valiant exon (v1-10) mentiioned in the reivew and variant exon what is mentioned above in the question is same? It seems from discussions that both are same. However, it is mentioned above that standard CD44 includes variant exon also which is of (1-742) is reflected also by the review. There must be some reason due to which size of CD44v is more than CD44. Might be due to post translational modifications of variant/valiant region, which is not part of this review. Such modifications might not be happening in the standard CD44 but be happening in the vCD44 based on the conditions. This could be the possible reason (yet to be proved) due to which CD44v is showing more molecular weight than CD44.
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