1oqm

<table><tr><td colspan='2'>[[1oqm]] is a 4 chain structure with sequence from [http://en.wikipedia.org/wiki/Bovin Bovin] and [http://en.wikipedia.org/wiki/Lk3_transgenic_mice Lk3 transgenic mice]. This structure supersedes the now removed PDB entry [http://oca.weizmann.ac.il/oca-bin/send-pdb?obs=1&id=1l7w 1l7w]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1OQM OCA]. For a <b>guided tour on the structure components</b> use [http://proteopedia.org/fgij/fg.htm?mol=1OQM FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=MN:MANGANESE+(II)+ION'>MN</scene>, <scene name='pdbligand=PG4:TETRAETHYLENE+GLYCOL'>PG4</scene>, <scene name='pdbligand=UD2:URIDINE-DIPHOSPHATE-N-ACETYLGALACTOSAMINE'>UD2</scene></td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Beta-N-acetylglucosaminylglycopeptide_beta-1,4-galactosyltransferase Beta-N-acetylglucosaminylglycopeptide beta-1,4-galactosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.38 2.4.1.38] </span></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://proteopedia.org/fgij/fg.htm?mol=1oqm FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1oqm OCA], [http://pdbe.org/1oqm PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1oqm RCSB], [http://www.ebi.ac.uk/pdbsum/1oqm PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1oqm ProSAT]</span></td></tr>

[[http://www.uniprot.org/uniprot/LALBA_MOUSE LALBA_MOUSE]] Regulatory subunit of lactose synthase, changes the substrate specificity of galactosyltransferase in the mammary gland making glucose a good acceptor substrate for this enzyme. This enables LS to synthesize lactose, the major carbohydrate component of milk. In other tissues, galactosyltransferase transfers galactose onto the N-acetylglucosamine of the oligosaccharide chains in glycoproteins. [[http://www.uniprot.org/uniprot/B4GT1_BOVIN B4GT1_BOVIN]] The Golgi complex form catalyzes the production of lactose in the lactating mammary gland and could also be responsible for the synthesis of complex-type N-linked oligosaccharides in many glycoproteins as well as the carbohydrate moieties of glycolipids. The cell surface form functions as a recognition molecule during a variety of cell to cell and cell to matrix interactions, as those occurring during development and egg fertilization, by binding to specific oligosaccharide ligands on opposing cells or in the extracellular matrix.

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== Publication Abstract from PubMed ==

beta1,4-Galactosyltransferase I (Gal-T1) normally transfers Gal from UDP-Gal to GlcNAc in the presence of Mn(2+) ion. In the presence of alpha-lactalbumin (LA), the Gal acceptor specificity is altered from GlcNAc to Glc. Gal-T1 also transfers GalNAc from UDP-GalNAc to GlcNAc, but with only approximately 0.1% of Gal-T activity. To understand this low GalNAc-transferase activity, we have carried out the crystal structure analysis of the Gal-T1.LA complex with UDP-GalNAc at 2.1-A resolution. The crystal structure reveals that the UDP-GalNAc binding to Gal-T1 is similar to the binding of UDP-Gal to Gal-T1, except for an additional hydrogen bond formed between the N-acetyl group of GalNAc moiety with the Tyr-289 side chain hydroxyl group. Elimination of this additional hydrogen bond by mutating Tyr-289 residue to Leu, Ile, or Asn enhances the GalNAc-transferase activity. Although all three mutants exhibit enhanced GalNAc-transferase activity, the mutant Y289L exhibits GalNAc-transferase activity that is nearly 100% of its Gal-T activity, even while completely retaining its Gal-T activity. The steady state kinetic analyses on the Leu-289 mutant indicate that the K(m) for GlcNAc has increased compared to the wild type. On the other hand, the catalytic constant (k(cat)) in the Gal-T reaction is comparable with the wild type, whereas it is 3-5-fold higher in the GalNAc-T reaction. Interestingly, in the presence of LA, these mutants also transfer GalNAc to Glc instead of to GlcNAc. The present study demonstrates that, in the Gal-T family, the Tyr-289/Phe-289 residue largely determines the sugar donor specificity.

Structure-based design of beta 1,4-galactosyltransferase I (beta 4Gal-T1) with equally efficient N-acetylgalactosaminyltransferase activity: point mutation broadens beta 4Gal-T1 donor specificity.,Ramakrishnan B, Qasba PK J Biol Chem. 2002 Jun 7;277(23):20833-9. Epub 2002 Mar 26. PMID:11916963<ref>PMID:11916963</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Beta-N-acetylglucosaminylglycopeptide beta-1,4-galactosyltransferase]]

[[Category: Bovin]]

[[Category: Lk3 transgenic mice]]

[[Category: Qasba, P K]]

[[Category: Ramakrishnan, B]]

[[Category: Udp-galnac]]