3cu0
human beta 1,3-glucuronyltransferase I (GlcAT-I) in complex with UDP and GAL-GAL(6-SO4)-XYL(2-PO4)-O-SER
Structural highlights
DiseaseB3GA3_HUMAN Defects in B3GAT3 are the cause of multiple joint dislocations short stature craniofacial dysmorphism and congenital heart defects (JDSSDHD) [MIM:245600. An autosomal recessive disease characterized by dysmorphic facies, bilateral dislocations of the elbows, hips, and knees, clubfeet, and short stature, as well as cardiovascular defects.[1] FunctionB3GA3_HUMAN Glycosaminoglycans biosynthesis. Involved in forming the linkage tetrasaccharide present in heparan sulfate and chondroitin sulfate. Transfers a glucuronic acid moiety from the uridine diphosphate-glucuronic acid (UDP-GlcUA) to the common linkage region trisaccharide Gal-beta-1,3-Gal-beta-1,4-Xyl covalently bound to a Ser residue at the glycosaminylglycan attachment site of proteoglycans. Can also play a role in the biosynthesis of l2/HNK-1 carbohydrate epitope on glycoproteins. Shows strict specificity for Gal-beta-1,3-Gal-beta-1,4-Xyl, exhibiting negligible incorporation into other galactoside substrates including Galbeta1-3Gal beta1-O-benzyl, Galbeta1-4GlcNAc and Galbeta1-4Glc. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSulfated glycosaminoglycans (GAGs), including heparan sulfate and chondroitin sulfate, are synthesized on the so-called common GAG-protein linkage region (GlcUAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser) of core proteins, which is formed by the stepwise addition of monosaccharide residues by the respective specific glycosyltransferases. Glucuronyltransferase-I (GlcAT-I) is the key enzyme that completes the synthesis of this linkage region, which is a prerequisite for the conversion of core proteins to functional proteoglycans bearing GAGs. The Xyl and Gal residues in the linkage region can be modified by phosphorylation and sulfation, respectively, although the biological significance of these modifications remains to be clarified. Here we present evidence that these modifications can significantly influence the catalytic activity of GlcAT-I. Enzyme assays showed that the synthetic substrates, Gal-Gal-Xyl(2-O-phosphate)-O-Ser and Gal-Gal(6-O-sulfate)-Xyl(2-O-phosphate)-O-Ser, served as better substrates than the unmodified compound, whereas Gal(6-O-sulfate)-Gal-Xyl(2-O-phosphate)-O-Ser exhibited no acceptor activity. The crystal structure of the catalytic domain of GlcAT-I with UDP and Gal-Gal(6-O-sulfate)-Xyl(2-O-phosphate)-O-Ser bound revealed that the Xyl(2-O-phosphate)-O-Ser is disordered and the 6-O-sulfate forms interactions with Gln(318) from the second GlcAT-I monomer in the dimeric enzyme. The results indicate the possible involvement of these modifications in the processing and maturation of the growing linkage region oligosaccharide required for the assembly of GAG chains. 2-o-phosphorylation of xylose and 6-o-sulfation of galactose in the protein linkage region of glycosaminoglycans influence the glucuronyltransferase-I activity involved in the linkage region synthesis.,Tone Y, Pedersen LC, Yamamoto T, Izumikawa T, Kitagawa H, Nishihara J, Tamura J, Negishi M, Sugahara K J Biol Chem. 2008 Jun 13;283(24):16801-7. Epub 2008 Apr 9. PMID:18400750[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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