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447 a.a.
_CA
_MN
 UDP-N-acetyl-D-galactosamine |
+ |
 polypeptide |
= |
 UDP |
+ |
N-acetyl-D- galactosaminyl-polypeptide |
|---|
Key reference
DOI no: 10.1073/pnas.0405657101 Proc Natl Acad Sci U S A 101:15307-15312 (2004) PubMed id: 15486088
The beginnings of mucin biosynthesis: the crystal structure of UDP-GalNAc:polypeptide alpha-N-acetylgalactosaminyltransferase-T1. T.A.Fritz, J.H.Hurley, L.B.Trinh, J.Shiloach, L.A.Tabak. ABSTRACT
UDP-GalNAc:polypeptide alpha-N-acetylgalactosaminyltransferases (ppGaNTases) initiate the formation of mucin-type, O-linked glycans by catalyzing the transfer of alpha-N-acetylgalactosamine from UDP-GalNAc to Ser or Thr residues of core proteins to form the Tn antigen (GalNAc-alpha-1-O-Ser/Thr). ppGaNTases are unique among glycosyltransferases in containing a C-terminal lectin domain. We present the x-ray crystal structure of a ppGaNTase, murine ppGaNTase-T1, and show that it folds to form distinct catalytic and lectin domains. The association of the two domains forms a large cleft in the surface of the enzyme that contains a Mn2+ ion complexed by invariant D209 and H211 of the "DXH" motif and by invariant H344. Each of the three potential lectin domain carbohydrate-binding sites (alpha, beta, and gamma) is located on the active-site face of the enzyme, suggesting a mechanism by which the transferase may accommodate multiple conformations of glycosylated acceptor substrates. A model of a mucin 1 glycopeptide substrate bound to the enzyme shows that the spatial separation between the lectin alpha site and a modeled active site UDP-GalNAc is consistent with the in vitro pattern of glycosylation observed for this peptide catalyzed by ppGaNTase-T1. The structure also provides a template for the larger ppGaNTase family, and homology models of several ppGaNTase isoforms predict dramatically different surface chemistries consistent with isoform-selective acceptor substrate recognition.
Selected figure(s)
Figure 2.
Fig. 2. The mppGaNTase-T1 structure preserves the uridine-binding domain (UBD) and ricin B chain topologies. (A) Topology diagram for mppGaNTase-T1. Coloring and numbering for the helices and strands are as in Fig. 1. The dashed line represents residues 347-358, for which electron density was not observed. (B) Topology diagram of the UBD of1,4-N-acetylglucosaminyltransferase (PDB ID code 1FO9 [PDB] ). The gray shaded areas in A and B denote the topology comprising the UBD. (C) Topology diagram for residues 1-135 of the ricin B chain.
Figure 3.
Fig. 3. Identification of potential UDP-GalNAc-binding residues. The figure shows selected residues of superimposed structures of mppGaNTase-T1 and EXTL2 (PDB ID code 1OMZ [PDB] ). Residues 207-213 of mppGaNTase-T1 containing the DXH motif and residues 149-155 of EXTL2 containing the DXD motif were aligned, followed by the Improve Fit option of SWISSPDBVIEWER. Residues of mppGaNTase-T1 within4Åofthe modeled UDP-GalNAc (atomic colors with white carbons) were identified by using the program CONTACT and are shown in atomic coloring with yellow carbons. Residues of EXTL2 are shown in white with white numbering. The Mn2+ ion bound to mppGaNTase-T1 is shown in red, and hydrogen bonds between it and residues D209 (2.42 Å), H211 (2.04 Å), and H344 (2.34 Å) are shown by the green dashed lines.Figures were selected by the author.
Literature references that cite this PDB file's key reference
PubMed id Reference
19292877 H.Hemmi, A.Kuno, S.Ito, R.Suzuki, T.Hasegawa, and J.Hirabayashi (2009).
NMR studies on the interaction of sugars with the C-terminal domain of an R-type lectin from the earthworm Lumbricus terrestris.FEBS J, 276, 2095-2105.
18562306 J.Raman, T.A.Fritz, T.A.Gerken, O.Jamison, D.Live, M.Liu, and L.A.Tabak (2008).
The catalytic and lectin domains of UDP-GalNAc:polypeptide alpha-N-Acetylgalactosaminyltransferase function in concert to direct glycosylation site selection.J Biol Chem, 283, 22942-22951.
18518825 L.L.Lairson, B.Henrissat, G.J.Davies, and S.G.Withers (2008).
Glycosyltransferases: structures, functions, and mechanisms.Annu Rev Biochem, 77, 521-555.
18669915 T.A.Gerken, K.G.Hagen, and O.Jamison (2008).
Conservation of peptide acceptor preferences between Drosophila and mammalian polypeptide-GalNAc transferase ortholog pairs.Glycobiology, 18, 861-870.
17697098 M.L.Klement, L.Ojemyr, K.E.Tagscherer, G.Widmalm, and A.Wieslander (2007).
A processive lipid glycosyltransferase in the small human pathogen Mycoplasma pneumoniae: involvement in host immune response.Mol Microbiol, 65, 1444-1457.
17970754 M.Tenno, A.Saeki, A.P.Elhammer, and A.Kurosaka (2007).
Function of conserved aromatic residues in the Gal/GalNAc-glycosyltransferase motif of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 1.FEBS J, 274, 6037-6045.
16385447 D.B.Sparrow, G.Chapman, M.A.Wouters, N.V.Whittock, S.Ellard, D.Fatkin, P.D.Turnpenny, K.Kusumi, D.Sillence, and S.L.Dunwoodie (2006).
Mutation of the LUNATIC FRINGE gene in humans causes spondylocostal dysostosis with a severe vertebral phenotype.Am J Hum Genet, 78, 28-37.
16033536 F.J.Irazoqui, V.G.Sendra, R.D.Lardone, and G.A.Nores (2005).
Immune response to Thomsen-Friedenreich disaccharide and glycan engineering.Immunol Cell Biol, 83, 405-412. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time.
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