Selectivity of von Willebrand factor triplet bands towards heparin bindingsupports structural model

Human plasma-derived von Willebrand factor (hp-vWF) and recombinant von Wil lebrand factor (r-vWF) have been fractionated by heparin affinity chromatog raphy followed by multimer analysis using SDS-agarose gel electrophoresis. Because heparin binding sites are contained in each VWF subunit, high molec ular weight multimers of r-vWF and hp-vWF, respectively, were eluted with h igher salt concentration, in comparison to r-vWF and hp-vWF molecules with a low degree of multimerization. Heparin affinity chromatography did not af fect the multimer composition of r-vWF. By contrast, faster migrating satel lite bands and slower migrating satellite bands of hp-vWF exhibited reduced and increased heparin affinity, respectively, compared to the intermediate band of the same triplet. Because heparin binding sites are localised in t he N-terminal domain of the hp-vWF subunit, this result confirms a structur al model of hp-vWF (Fischer et al., Biochem. J. 1998;331:483-488) suggested recently, in which the slower migrating satellite bands have excess of one N-terminal fragment and the faster migrating satellite bands lack one N-te rminal fragment, respectively, in comparison with the corresponding interme diate triplet band.