Fig. 6. UDP binding sites in EXTL3.

Purified EXTL3∆N was incubated with UDP and subjected to cryo-EM single particle analysis in order to determine its structure. No density for UDP was visible in the GT47 domain. a Residues involved in binding UDP and Mn²⁺ in mouse EXTL2 and the GT64 domain of human EXTL3. Human EXTL3 (in complex with UDP and Mn²⁺) is shown in blue (phosphates in orange). Mouse EXTL2 (in complex with UDP-GlcNAc and Mn²⁺; PDB: 1ON6) is shown in tan. b The GT64 active site and the apparently inactivated GT47 nucleotide binding site are separated by a substantial distance. The DxD motif and bound UDP of the GT64 domain are shown in blue. The Cα3 and Cα4 helices of the GT47 domain are shown in dark grey. The side chain of Glu453 is shown in stick representation.