The molecular mechanics of P- and L-selectin lectin domains binding to PSGL-1.
A laser trap was used to compare the load-dependent binding kinetics between truncated P- and L-selectin to their natural ligand, P-selectin glycoprotein ligand-1 (PSGL-1) over the predicted physiological range of loading rates. Human PSGL-1 was covalently coupled to polystyrene beads. Chimeric selectins were adsorbed to nitrocellulose-coated glass beads on a coverslip. A PSGL-1 bead was held in a laser trap and touched to a vertical surface of the glass bead, allowing a bond to form between selectin and ligand. The surface was moved away from the microsphere, applying load at a constant rate until bond rupture. Rupture force for both selectins increased with loading rate, but significant differences in rupture force between P- and L-selectin were observed only above 460 pN/s. These data are best represented as two energy barriers to unbinding, with the transition from the low to high loading rate regime at 260-290 pN/s. The data also allow the first estimate of a two-dimensional specific on-rate for binding of these two selectins to their natural ligand (1.7 microm2/s). These data suggest that P- and L-selectin lectin domains have very similar kinetics under physiological conditions.
Rinko
Linda J
LJ
Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908, USA.
Lawrence
Michael B
MB
Guilford
William H
WH
D001665:Binding Sites; D001696:Biomechanical Phenomena / Q000379:methods; D019041:L-Selectin / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008846:Micromanipulation / Q000379:methods; D009038:Motion; D019007:P-Selectin / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D019087:Selectins / Q000737:chemistry; D013718:Tensile Strength
D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D019087:Selectins; D019041:L-Selectin