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CD44 variant exon v5 encodes a tyrosine that is sulphated
J P Sleeman1, U Rahmsdorf, A Steffen
1Forschungszentrum Karlsruhe, Institute of Genetics, Germany. sleeman@igen.fzk.de
European Journal of Biochemistry
|August 6, 1998
Summary
Tyrosine sulfation of CD44 variant proteins, specifically exon v5, occurs in vivo. This post-translational modification may influence CD44
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- CD44 glycoproteins exhibit functional diversity due to post-translational modifications and alternative splicing.
- Tyrosine sulfation, a modification enhancing protein-protein interactions, occurs in various protein types.
Purpose of the Study:
- To investigate the role of tyrosine sulfation in CD44 protein function.
- To identify the specific site and mechanism of tyrosine sulfation in CD44 variants.
Main Methods:
- Identification of a tyrosine sulfation motif in rat and mouse CD44 exon v5.
- In vivo incorporation of inorganic sulfate into the CD44v4-v7 splice variant.
- Site-directed mutagenesis to alter the tyrosine residue in exon v5.
Main Results:
- A canonical tyrosine sulfation motif was identified in CD44 exon v5.
- Inorganic sulfate was confirmed to be incorporated into the metastasis-associated CD44v4-v7 splice variant.
- Mutation of the exon v5 tyrosine to phenylalanine abolished sulfate incorporation, confirming the motif's functionality in vivo.
Conclusions:
- The tyrosine sulfation motif in CD44 exon v5 is utilized in vivo.
- Sulfation occurs directly on the tyrosine residue, not via glycosaminoglycans.
- Exon v5 sulfation may play a role in mediating CD44 ligand binding activity.