1v83: Difference between revisions

[[Image:1v83.gif|left|200px]]<br /><applet load="1v83" size="350" color="white" frame="true" align="right" spinBox="true"  

The HNK-1 carbohydrate epitope is found on many neural cell adhesion molecules. Its structure is characterized by a terminal sulfated glucuronyl acid. The glucuronyltransferases, GlcAT-P and GlcAT-S, are involved in the biosynthesis of the HNK-1 epitope, GlcAT-P as the major enzyme. We overexpressed and purified the recombinant human GlcAT-P from Escherichia coli. Analysis of its enzymatic activity showed that it catalyzed the transfer reaction for N-acetyllactosamine (Galbeta1-4GlcNAc) but not lacto-N-biose (Galbeta1-3GlcNAc) as an acceptor substrate. Subsequently, we determined the first x-ray crystal structures of human GlcAT-P, in the absence and presence of a donor substrate product UDP, catalytic Mn(2+), and an acceptor substrate analogue N-acetyllactosamine (Galbeta1-4GlcNAc) or an asparagine-linked biantennary nonasaccharide. The asymmetric unit contains two independent molecules. Each molecule is an alpha/beta protein with two regions that constitute the donor and acceptor substrate binding sites. The UDP moiety of donor nucleotide sugar is recognized by conserved amino acid residues including a DXD motif (Asp(195)-Asp(196)-Asp(197)). Other conserved amino acid residues interact with the terminal galactose moiety of the acceptor substrate. In addition, Val(320) and Asn(321), which are located on the C-terminal long loop from a neighboring molecule, and Phe(245) contribute to the interaction with GlcNAc moiety. These three residues play a key role in establishing the acceptor substrate specificity.

1V83 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=MN:'>MN</scene>, <scene name='pdbligand=TLA:'>TLA</scene> and <scene name='pdbligand=UDP:'>UDP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Galactosylgalactosylxylosylprotein_3-beta-glucuronosyltransferase Galactosylgalactosylxylosylprotein 3-beta-glucuronosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.135 2.4.1.135] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1V83 OCA].  

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