Fig. 5: Heparan sulfate chain elongation is nonprocessive.
From: Structure of the human heparan sulfate polymerase complex EXT1-EXT2
a Surface representation of the EXT1-EXT2 complex. The metal-ion dependence of the GlcNAc-T reaction is indicated by small spheres with a Mn2+ label. A red cross illustrates that the pseudo-GlcA-T domain of EXT2 is catalytic inactive. Distances between the EXT1 GlcA-T active site and the GlcNAc-T active sites of EXT1 and EXT2 are marked by a yellow dotted line. b Time course experiment using an excess of fluorescently-labeled oligosaccharide (dp8) substrate and limiting amounts of purified EXT1-EXT2 complex. A ladder-like pattern suggests that GlcNAc and GlcA addition by the EXT1-EXT2 complex occur in a step-wise fashion. Source data is provided as a Source Data 7. GlcNAc-T, N-Acetylglucosamine-transferase; GlcA-T, glucuronic acid-transferase.
