References

1. Visualization of P-selectin Glycoprotein Ligand-1 as a Highly Extended Molecule and Mapping of Protein Epitopes for Monoclonal Antibodies
2. Post-translational Modifications of Recombinant P-selectin Glycoprotein Ligand-1 Required for Binding to P- and E-selectin
3. Structures of the O-Glycans on P-selectin Glycoprotein Ligand-1 from HL-60 Cells
4. Tyrosine Sulfation of P-selectin Glycoprotein Ligand-1 Is Required for High Affinity Binding to P-selectin

They have shown that for the interaction with P-selectin the PSGL 1 molecule must be dimeric, express the sialyl-Le^x epitope and also carry orther post-translational modifications. They have proposed the following domain structure for the molecule

In particular the binding of monoclonal antibody PL1 which specifically blocks interaction with P selectin has been shown to be dependent on tyrosine sulphation as well as an O-glycan with the sialyl-Le^x epitope. The predicted binding site on PSGL-1 determined by their wrk is shown below.

The group has also studied the O-glycans present on the native molecule and have found the following structures which express the sialyl-Le^x epitope