Cell-surface heparan sulfate: an intercalated membrane proteoglycan.

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Abstract
Two pools of heparan sulfate proteoglycans were selectively solubilized from rat liver plasma membranes by successive incubatins with heparin and detergent. The 2 populations of proteoglycans have similar polyanionic properties as indicated by identical elution positions on ion-exchange chromatography on DEAE-Sephacel but differ in buoyant density in CsCl when analyzed by density gradient centrifugation in the presence of 4 M guanidine. The detergent-extracted proteoglycan has a lower buoyant density (.ltoreq. 1.40 g/ml) and is, as determined by gel chromatography, slightly larger than the heparin-released proteoglycan (buoyant density, .gtoreq. 1.55 g/ml). Furthermore, in contrast to the heparin-released proteoglycan, the detergent extracted proteoglycan is able to bind detergent micelles, shows affinity for the hydrophobic gel octyl-Sepharose and can be inserted into liposomes. The detergent-extracted heparan sulfate probably represents a proteoglycan species that has its core protein rooted in the lipid bilayer of the plasma membrane.