| First Author | Pak JE | Year | 2011 |
| Journal | J Mol Biol | Volume | 414 |
| Issue | 5 | Pages | 798-811 |
| PubMed ID | 22056345 | Mgi Jnum | J:320698 |
| Mgi Id | MGI:6879401 | Doi | 10.1016/j.jmb.2011.10.039 |
| Citation | Pak JE, et al. (2011) Structural and mechanistic characterization of leukocyte-type core 2 beta1,6-N-acetylglucosaminyltransferase: a metal-ion-independent GT-A glycosyltransferase. J Mol Biol 414(5):798-811 |
| abstractText | Leukocyte-type core 2 beta1,6-N-acetylglucosaminyltransferase (C2GnT-L) is an inverting, metal-ion-independent glycosyltransferase that catalyzes the formation of mucin-type core 2 O-glycans. C2GnT-L belongs to the GT-A fold, yet it lacks the metal ion binding DXD motif characteristic of other nucleoside disphosphate GT-A fold glycosyltransferases. To shed light on the basis for its metal ion independence, we have solved the X-ray crystal structure (2.3 A resolution) of a mutant form of C2GnT-L (C217S) in complex with the nucleotide sugar product UDP and, using site-directed mutagenesis, examined the roles of R378 and K401 in both substrate binding and catalysis. The structure shows that C2GnT-L exists in an "open" conformation and a "closed" conformation and that, in the latter, R378 and K401 interact with the beta-phosphate moiety of the bound UDP. The two conformations are likely to be important in catalysis, but the conformational changes that lead to their interconversion do not resemble the nucleotide-sugar-mediated loop ordering observed in other GT-A glycosyltransferases. R378 and K401 were found to be important in substrate binding and/or catalysis, an observation consistent with the suggestion that they serve the same role played by metal ion in all of the other GT-A glycosyltransferases studied to date. Notably, R378 and K401 appear to function in a manner similar to that of the arginine and lysine residues contained in the RX(4-5)K motif found in the retaining GT-B glycosyltransferases. |
