Self-association of heparan sulfate. Demonstration of binding by affinity chromatography of free chains on heparan sulfate-substituted agarose gels.

We have developed an affinity chromatography procedure which measures binding of heparan sulfate species to agarose gels substituted with different heparan sulfates. Three major subfractions of bovine lung heparan sulfate (HS2, HS3, and HS4) which differ in sulfate content and hexuronate composition have been used. Association-prone variants of these species (HS2-A, HS3-A, and HS4-A) were prepared by gel chromatography. Free heparan sulfate chains were applied to columns of various heparan sulfate-agaroses which were eluted with a linear guanidine gradient and binding was assessed by measuring the hexuronate content of the effluent. Associating heparan sulfate of a particular subfraction was chiefly bound to gels that were substituted with chains of the same kind, i.e. HS2-A to HS2-A-agarose, HS3-A and HS4-A to HS3-A-agarose, and HS4-A to HS4-A-agarose. N-Desulfation and N-acetylation of HS2-A markedly reduced binding to HS2-A-agarose and periodate oxidation of glucuronate in HS3-A completely abolished binding to HS3-A-agarose. Partially oxidized HS2-A was separated into bound and unbound material by affinity chromatography on HS2-A-agarose. Gel chromatography of these fractions indicated that unbound chains were significantly smaller than bound ones. It is concluded that association between heparan sulfate chains may be quite specific and that the strength of binding is dependent on co-operative interactions between a number of contact zones. The latter may correspond to the N-sulfated and iduronate- and glucuronate-containing segments.