High molecular-weight heparan sulfate from the cell surface

Heparan sulfate fragments with molecular weight of 135,000 (as determined by equilibrium sedimentation analysis) were isolated from the trypsinate of Chinese hamster cells (line CHO) grown in culture. Evidence is presented which suggests that the intracellular heparan sulfate species with molecular weight of 10,000 to 20,000 were degradation products of the larger species. We propose that the native cell-surface heparan sulfate, in its physiological location, could serve as a nonspecific “screen” to the exposure of specific, topographically adjacent, cell-surface sites.