Heterogeneous distribution of antithrombin-binding sites in rat brain heparan sulphate proteoglycans.
Heparan sulphates with high binding affinity for antithrombin (HA-HS), labelled in vivo with [35S]sulphate, were extracted from rat brains and purified by chromatography on DEAE-cellulose and on antithrombin-agarose. HA-HS proteoglycans (HA-HSPG) were then separated from HA-HS chains on Sepharose CL-6B. The total HA-HSPG product was rechromatographed on antithrombin-agarose. Six HA-HSPG subfractions with differing degrees of affinity for antithrombin were recovered and treated with NaOH to release their chains. Rechromatography of these six 35S-labelled HS chain preparations on antithrombin-agarose showed that their proportions of chains with no affinity for antithrombin (NA-HS chains) ranged from 36 to 71%. There was a reciprocal relationship between the proportion of NA-HS chains in each HA-HSPG subfraction and the degree of affinity for antithrombin of the rest of its chains (assessed relative to 3H-labelled HA-heparin chains with which they were co-chromatographed). Similar characteristics of antithrombin-binding-site distribution apply to HA-heparin proteoglycans from rat skin studied previously [Horner (1987) Biochem. J. 244, 693-698]. The data suggest that the sites at which 3-O-sulphation of some glucosamine N-sulphate residues occurs in the Golgi complex of brain cells (probably endothelial cells) which synthesize HA-HSPGs (as in mast cells, which synthesize HA-heparin PGs) are distributed sparsely but not randomly.
Horner
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AA
Department of Physiology, University of Toronto, Ont., Canada.
D000818:Animals; D000991:Antithrombins / Q000378:metabolism*; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D002853:Chromatography, Liquid; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000378:metabolism*; D008297:Male; D011509:Proteoglycans / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000991:Antithrombins; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D011509:Proteoglycans