The Solution Structure of Heparan Sulfate Differs from That of Heparin

Abstract

The highly sulfated polysaccharides heparin and heparan sulfate (HS) play key roles in the regulation of physiological and pathophysiological processes. Despite its importance, no molecular structures of free HS have been reported up to now. By combining analytical ultracentrifugation, small angle x-ray scattering, and constrained scattering modeling recently used for heparin, we have analyzed the solution structures for eight purified HS fragments degree of polymerization 6 -18 (dp6 -dp18) and dp24, corresponding to the predominantly unsulfated GlcA-GlcNAc domains of heparan sulfate. Unlike heparin, the sedimentation coefficient s 20,w of HS dp6 -dp24 showed a small rotor speed dependence, where similar s 20,w values of 0.82-1.26 S (absorbance optics) and 1.05-1.34 S (interference optics) were determined. The corresponding x-ray scattering measurements of HS dp6 -dp24 gave radius of gyration (R G ) values from 1.03 to 2.82 nm, cross-sectional radius of gyration (R XS ) values from 0.31 to 0.65 nm, and maximum lengths (L) from 3.0 to 10.0 nm. These data showed that HS has a longer and more bent structure than heparin. Constrained scattering modeling starting from 5000 -8000 conformationally randomized HS structures gave best fit dp6 -dp16 molecular structures that were longer and more bent than their equivalents in heparin. No fits were obtained for HS dp18 or dp24, indicating their higher flexibility. We conclude that HS displays an extended bent conformation that is significantly distinct from that for heparin. The difference is attributed to the different predominant monosaccharide sequence and reduced sulfation of HS, indicating that HS may interact differently with proteins compared with heparin.

Large-Scale Investigation of Leishmania Interaction Networks with Host Extracellular Matrix by Surface Plasmon Resonance Imaging

“…This might be due to differences in the structures of these glycosaminoglycans. Heparan sulfate is less sulfated than heparin, contains clustered sulfate groups organized in highly sulfated domains, and has a longer and more bent conformation than heparin (37). It is thus not relevant to automatically infer from the experimentally proven ability of Leishmania parasites to bind heparin that they also bind to heparan sulfate and to heparan sulfate proteoglycans at the host cell surface and that these proteoglycans play a role in Leishmania adhesion to and/or entry into host cells.…”

Pharmacology of Heparin and Related Drugs

“…Recent studies have, however, raised the possibility that a significant deviation from this conformation is a possibility in some circumstances (Hricovíni, 2011;Sattelle and Almond, 2011). Two recent studies, one using 15 N NMR and one using analytical ultracentrifugation (Mobli et al, 2008;Khan et al, 2012Khan et al, , 2013, indicate that the NA domains have sufficient flexibility to allow adoption of a wide variety of curved and bent configurations.…”

Crystal Structure of N-Glycosylated Human Glypican-1 Core Protein

“…An HS chain can consist of up to 50 -100 repeating disaccharide units of GlcNAc and GlcA. From the solution structure of HS, the length of an HS chain consisting of eight disaccharide units has been estimated to be around 70 Å (47). Thus, a full HS chain can be ϳ500 Å long, as compared with the 100 Å for the folded glypican core protein.…”