X-ray crystal structure of leukocyte type core 2 beta1,6-N-acetylglucosaminyltransferase. Evidence for a convergence of metal ion-independent glycosyltransferase mechanism
| Autor: | John E, Pak, Pascal, Arnoux, Sihong, Zhou, Prashanth, Sivarajah, Malathy, Satkunarajah, Xuekun, Xing, James M, Rini |
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| Rok vydání: | 2006 |
| Předmět: |
Ions
Models Molecular Binding Sites Recombinant Fusion Proteins Molecular Sequence Data Oligosaccharides Crystallography X-Ray N-Acetylglucosaminyltransferases Protein Structure Tertiary Substrate Specificity Mice Metals Polysaccharides Uridine Diphosphate Glucuronic Acid Animals Amino Acid Sequence Sequence Alignment |
| Zdroj: | The Journal of biological chemistry. 281(36) |
| ISSN: | 0021-9258 |
| Popis: | Leukocyte type core 2 beta1,6-N-acetylglucosaminyltransferase (C2GnT-L) is a key enzyme in the biosynthesis of branched O-glycans. It is an inverting, metal ion-independent family 14 glycosyltransferase that catalyzes the formation of the core 2 O-glycan (Galbeta1-3[GlcNAcbeta1-6]GalNAc-O-Ser/Thr) from its donor and acceptor substrates, UDP-GlcNAc and the core 1 O-glycan (Galbeta1-3GalNAc-O-Ser/Thr), respectively. Reported here are the x-ray crystal structures of murine C2GnT-L in the absence and presence of the acceptor substrate Galbeta1-3GalNAc at 2.0 and 2.7A resolution, respectively. C2GnT-L was found to possess the GT-A fold; however, it lacks the characteristic metal ion binding DXD motif. The Galbeta1-3GalNAc complex defines the determinants of acceptor substrate binding and shows that Glu-320 corresponds to the structurally conserved catalytic base found in other inverting GT-A fold glycosyltransferases. Comparison of the C2GnT-L structure with that of other GT-A fold glycosyltransferases further suggests that Arg-378 and Lys-401 serve to electrostatically stabilize the nucleoside diphosphate leaving group, a role normally played by metal ion in GT-A structures. The use of basic amino acid side chains in this way is strikingly similar to that seen in a number of metal ion-independent GT-B fold glycosyltransferases and suggests a convergence of catalytic mechanism shared by both GT-A and GT-B fold glycosyltransferases. |
| Databáze: | OpenAIRE |
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