A LIQUID-PHASE BINDING ANALYSIS FOR L-SELECTIN - A STRONG DEPENDENCY ON HIGHLY CLUSTERED SULFATE GROUPS

L-selectin, together with E- and P-selectins, forms a newer group of c ell adhesion molecules which are believed to interact with carbohydrat e ligands [Lasky, L. A., Singer, M. S., Yednoch, T. A., Dowbenko, D., Fennie, C., Rodriguez, H., Nguyen, T, Stachel, S. and Rosen, S. D. (19 89) Cell 56, 1045-1055]. Using radiolabeled fucoidan as a reference li gand, we have developed a new liquid-phase microcentrifugation assay w here fine differences in binding affinity can be compared accurately. We found that glucan sulfates strongly inhibited the binding of fucoid an by murine L-selectin-IgG chimera. The efficacy of inhibition is ext remely dependent on the size (up to 12 kDa) and the sulfate density (u p to two sulfate groups/glucose molecule) of the glucan sulfates. The nature of the inter-glucose linkages is also important. These data sug gest that the binding by L-selectin prefers certain clustering and pro per spatial arrangement of the anionic groups.