X-ray Crystal Structure of Leukocyte Type Core 2 β1 ,6-N-Acetylglucosaminyltransferase.
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| Title: | X-ray Crystal Structure of Leukocyte Type Core 2 β1 ,6-N-Acetylglucosaminyltransferase. |
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| Authors: | Pak, John E.1, Arnoux, Pascal1, Sihong Zhou1, Sivarajah, Prashanth1, Satkunarajah, Malathy1, Xuekun Xing1, Rini, James M.1 james.rini@utoronto.ca |
| Source: | Journal of Biological Chemistry. 9/8/2006, Vol. 281 Issue 36, p26693-26701. 9p. 6 Diagrams, 1 Chart. |
| Subjects: | X-ray crystallography, Biosynthesis, Leukocytes, Glycosyltransferases, Glucans, Nucleosides, Biochemistry |
| Abstract: | Leukocyte type core 2 β1,6-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 (Galβ1-3[GlcNAcβ1-6]GalNAc-O-Ser/Thr) from its donor and acceptor substrates, UDP-GIcNAc and the core 1 O-glycan (Galβ1-3GalNAc-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 Galβ1-3GalNAc at 2.0 and 2.7 Å resolution, respectively. C2GnT-L was found to possess the GT-A fold; however, it lacks the characteristic metal ion binding DXD motif. The Galβ1-3GalNAc 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 disphosphate 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. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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