PHOSPHORYLATION OF RECOMBINANT N-SYNDECAN (SYNDECAN-3) CORE PROTEIN

The cytoplasmic domain of the syndecan family of heparan sulfate prote oglycans is punctuated by the presence of four regularly spaced tyrosi ne residues. In this report, we explore the possibility of whether the four tyrosine residues in the cytoplasmic domain of N-syndecan (Synde can 3) are potential substrates for phosphorylation by a tyrosine kina se. Bacterially expressed elh kinase was used to phosphorylate a serie s of bacterially expressed N-syndecan fusion proteins. Our results cle arly demonstrate that the tyrosine residues in the cytoplasmic domain of N-syndecan can be phosphorylated by a tyrosine-specific kinase, and that all four tyrosine residues are capable of being phosphorylated. (C) 1997 Academic Press.