View source for 1ns2

==Crystal structure of galactose mutarotase from Lactococcus lactis mutant E304A complexed with galactose==
<StructureSection load='1ns2' size='340' side='right' caption='[[1ns2]], [[Resolution|resolution]] 1.95&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1ns2]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Lactococcus_lactis Lactococcus lactis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NS2 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1NS2 FirstGlance]. <br>
</td></tr><tr><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=GAL:BETA-D-GALACTOSE'>GAL</scene>, <scene name='pdbligand=NI:NICKEL+(II)+ION'>NI</scene><br>
<tr><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1ns0|1ns0]], [[1ns4|1ns4]], [[1ns7|1ns7]], [[1ns8|1ns8]], [[1nsm|1nsm]], [[1nsr|1nsr]], [[1nss|1nss]], [[1nsu|1nsu]], [[1nsv|1nsv]], [[1nsx|1nsx]], [[1nsz|1nsz]]</td></tr>
<tr><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Aldose_1-epimerase Aldose 1-epimerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.1.3.3 5.1.3.3] </span></td></tr>
<tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1ns2 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ns2 OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1ns2 RCSB], [http://www.ebi.ac.uk/pdbsum/1ns2 PDBsum]</span></td></tr>
<table>
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/ns/1ns2_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/chain_selection.php?pdb_ID=2ata ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Galactose mutarotase catalyzes the first step in normal galactose metabolism by catalyzing the conversion of beta-D-galactose to alpha-D-galactose. The structure of the enzyme from Lactococcus lactis was recently solved in this laboratory and shown to be topologically similar to domain 5 of beta-galactosidase. From this initial X-ray analysis, four amino acid residues were demonstrated to be intimately involved in sugar binding to the protein: His 96, His 170, Asp 243, and Glu 304. Here we present a combined X-ray crystallographic and kinetic analysis designed to examine the role of these residues in the reaction mechanism of the enzyme. For this investigation, the following site-directed mutant proteins were prepared: H96N, H170N, D243N, D243A, E304Q, and E304A. All of the structures of these proteins, complexed with either glucose or galactose, were solved to a nominal resolution of 1.95 A or better, and their kinetic parameters were measured against D-galactose, D-glucose, L-arabinose, or D-xylose. From these studies, it can be concluded that Glu 304 and His 170 are critical for catalysis and that His 96 and Asp 243 are important for proper substrate positioning within the active site. Specifically, Glu 304 serves as the active site base to initiate the reaction by removing the proton from the C-1 hydroxyl group of the sugar substrate and His 170 functions as the active site acid to protonate the C-5 ring oxygen.

The catalytic mechanism of galactose mutarotase.,Thoden JB, Kim J, Raushel FM, Holden HM Protein Sci. 2003 May;12(5):1051-9. PMID:12717027<ref>PMID:12717027</ref>

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

==See Also==
*[[Galactose mutarotase|Galactose mutarotase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Aldose 1-epimerase]]
[[Category: Lactococcus lactis]]
[[Category: Holden, H M.]]
[[Category: Thoden, J B.]]
[[Category: Epimerase]]
[[Category: Galactose metabolism]]
[[Category: Isomerase]]
[[Category: Mutarotase]]