Selectins and their ability to interact with specific
ligands are
a cornerstone in cell communication. Over the last three decades,
a considerable wealth of experimental and molecular modeling insights
into their structure and modus operandi were gathered.
Nonetheless, explaining the role of individual selectin residues on
a quantitative level remained elusive, despite its importance in understanding
the structure–function relationship in these molecules and
designing their inhibitors. This work explores essential interactions
of selectin–ligand binding, employing a multiscale approach
that combines molecular dynamics, quantum-chemical calculations, and
residue interaction network models. Such an approach successfully
reproduces most of the experimental findings. It proves to be helpful,
with the potential for becoming an established tool for quantitative
predictions of residue contribution to the binding of biomolecular
complexes. The results empower us to quantify the importance of particular
residues and functional groups in the protein–ligand interface
and to pinpoint differences in molecular recognition by the three
selectins. We show that mutations in the E-, L-, and P-selectins,
e.g., different residues in positions 46, 85, 97, and 107, present
a crucial difference in how the ligand is engaged. We assess the role
of sulfation of tyrosine residues in PSGL-1 and suggest that TyrSO3
– in position
51 interacting with Arg85 in P-selectin is a significant factor in
the increased affinity of P-selectin to PSGL-1 compared to E- and
L-selectins. We propose an original pharmacophore targeting five essential
PSGL-binding sites based on the analysis of the selectin···PSGL-1
interactions.