Serine phosphorylation of syndecan-2 proteoglycan cytoplasmic domain.

Protein kinase C (PKC) is involved in cell-matrix and cell-cell adhesion, and the cytoplasmic domain of syndecan-2 contains two serines (residues 197 and 198) which lie in a consensus sequence for phosphorylation by PKC. Other serine and threonine residues are present but not in a consensus sequence. We investigated phosphorylation ...
of syndecan-2 cytoplasmic domain by PKC, using purified GST-syndecan-2 fusion proteins and synthetic peptides corresponding to regions of the cytoplasmic domain. A synthetic peptide encompassing the entire cytoplasmic domain of syndecan-2 was phosphorylated by PKC with high affinity. Peptide mapping and substitution studies showed that both serines were phosphoacceptors, but each had slightly different affinity, with that of serine-197 being higher than serine-198. The efficiency of phosphorylation was concentration-dependent. At low concentrations, the cytoplasmic domain peptides were monomeric, with 2 mol/mol serine phosphorylation. At higher concentrations, however, the peptides formed dimers, with only 0.5 mol/mol phosphorylation. Concentration-dependent dimerization was not altered by phosphorylation. Phosphorylation is, therefore, dependent on the conformation of syndecan-2 cytoplasmic domain, but does not affect its oligomeric status.
Mesh Terms:
Amino Acid Sequence, Blotting, Western, Chromatography, Gel, Chromatography, Thin Layer, Cytoplasm, Electrophoresis, Polyacrylamide Gel, Escherichia coli, Glutathione Transferase, Kinetics, Membrane Glycoproteins, Molecular Sequence Data, Peptide Fragments, Phosphates, Phosphopeptides, Phosphorylation, Phosphoserine, Protein Kinase C, Proteoglycans, Recombinant Fusion Proteins, Syndecan-2
Arch. Biochem. Biophys.
Date: Aug. 01, 1997
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