Endostatin is a naturally occurring proteolytic fragment of the C-terminal domain of collagen XVIII. It inhibits angiogenesis by a mechanism that appears to involve binding to HS (heparan sulphate). We have examined the molecular interaction between endostatin and HS from micro- and macrovessel endothelial cells. Two discrete panels of oligosaccharides were prepared from metabolically radiolabelled HS, using digestion with either heparinase I or III, and then examined for their endostatin affinity using a sensitive filter-binding assay. Two types of endostatin-binding regions were identified: one comprising sulphated domains of five or more disaccharides in length, enriched in 6-O-sulphate groups, and the other contained long heparinase I-resistant fragments. In the latter case, evidence from the present study suggests that the binding region encompasses a sulphated domain fragment and a transition zone of intermediate sulphation. The contribution to binding of specific O-sulphate groups was determined using selectively desulphated HS species, namely HS from Hs2st−/− mutant cells, and by comparing the compositions of endostatin-binding and non-binding oligosaccharides. The results indicate that 6-O-sulphates play a dominant role in site selectivity and 2-O-sulphates are not strictly essential.
Binding of endostatin to endothelial heparan sulphate shows a differential requirement for specific sulphates
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Fiona H. BLACKHALL, Catherine L. R. MERRY, Malcolm LYON, Gordon C. JAYSON, Judah FOLKMAN, Kashi JAVAHERIAN, John T. GALLAGHER; Binding of endostatin to endothelial heparan sulphate shows a differential requirement for specific sulphates. Biochem J 1 October 2003; 375 (1): 131–139. doi: https://doi.org/10.1042/bj20030730
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