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. 1998 Jul 13;142(1):129–138. doi: 10.1083/jcb.142.1.129

Figure 5.

Figure 5

Figure 5

The PDZ domain of hCASK binds to the COOH-terminal sequence of syndecans. (a) Alignment of the cytoplasmic domains of rat syndecan family members demonstrate the high degree of homology among the four proteins (reviewed in Bernfield et al., 1992). In particular, note the conservation of the last four residues (in bold), which in other proteins are known to determine PDZ tail-binding specificity. (b) Direct binding study with syn-2 peptide and hCASK PDZ fusion protein. Syn-2 peptide representing the last eight residues was coupled to CNBr- activated Sepharose beads. The beads with immobilized peptide were incubated with GST-PDZ recombinant fusion protein with increasing concentrations of syn-2 or syn-1 peptides (0–200 μM) in solution. Controls consisted of GST alone incubated with peptides immobilized on beads; GST-PDZ fusion protein with peptide-free Sepharose beads (Beads alone); and GST-PDZ fusion protein incubated with beads coupled to syn-2 peptide and 50 μM control dlg peptide in solution (Ctr). The dlg control peptide (KKKKETDV-COOH) has optimal binding affinity for murine Dlg PDZ domain (Songyang et al., 1997).