Binding of bovine prion protein to heparin: a fluorescence polarization study.

Glycosaminoglycans (GAGs) are believed to be associated with prion disease pathology and also with metabolism of the prion protein. Fluorescence polarization assay (FPA) of binding between bovine recombinant prion protein (brecPrP) and heparin labelled with AlexaFluor488 was used in model experiments to study glycosaminoglycan-prion protein interaction. Heparin binding to brecPrP was a rapid reversible event which occurred under defined conditions. The interaction of brecPrP with fluorophore-labelled heparin was inhibited by the presence of Cu(2+) ions and was sensitive to competition with heparin, heparan sulphate, and dextran. The dissociation constant of the heparin-brecPrP complex was 73.4+/-3.7 nM. Circular dichroism (CD) experiments indicated that the structure of brecPrP was less helical in the presence of heparin.