View source for 1m01

==Wildtype Streptomyces plicatus beta-hexosaminidase in complex with product (GlcNAc)==
<StructureSection load='1m01' size='340' side='right' caption='[[1m01]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1m01]] is a 1 chain structure with sequence from [http://en.wikipedia.org/wiki/Atcc_25483 Atcc 25483]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1M01 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1M01 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1m03|1m03]], [[1m04|1m04]], [[1hp5|1hp5]], [[1jak|1jak]]</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-acetylhexosaminidase Beta-N-acetylhexosaminidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.52 3.2.1.52] </span></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1m01 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1m01 OCA], [http://pdbe.org/1m01 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1m01 RCSB], [http://www.ebi.ac.uk/pdbsum/1m01 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/m0/1m01_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/main_output.php?pdb_ID=1m01 ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
SpHex, a retaining family 20 glycosidase from Streptomyces plicatus, catalyzes the hydrolysis of N-acetyl-beta-hexosaminides. Accumulating evidence suggests that the hydrolytic mechanism involves substrate-assisted catalysis wherein the 2-acetamido substituent acts as a nucleophile to form an oxazolinium ion intermediate. The role of a conserved aspartate residue (D313) in the active site of SpHex was investigated through kinetic and structural analyses of two variant enzymes, D313A and D313N. Three-dimensional structures of the wild-type and variant enzymes in product complexes with N-acetyl-d-glucosamine revealed substantial differences. In the D313A variant the 2-acetamido group was found in two conformations of which only one is able to aid in catalysis through anchimeric assistance. The mutation D313N results in a steric clash in the active site between Asn-313 and the 2-acetamido group preventing the 2-acetamido group from providing anchimeric assistance, consistent with the large reduction in catalytic efficiency and the insensitivity of this variant to chemical rescue. By comparison, the D313A mutation results in a shift in a shift in the pH optimum and a modest decrease in activity that can be rescued by using azide as an exogenous nucleophile. These structural and kinetic data provide evidence that Asp-313 stabilizes the transition states flanking the oxazoline intermediate and also assists to correctly orient the 2-acetamido group for catalysis. Based on analogous conserved residues in the family 18 chitinases and family 56 hyaluronidases, the roles played by the Asp-313 residue is likely general for all hexosaminidases using a mechanism involving substrate-assisted catalysis.

Aspartate 313 in the Streptomyces plicatus hexosaminidase plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state.,Williams SJ, Mark BL, Vocadlo DJ, James MN, Withers SG J Biol Chem. 2002 Oct 18;277(42):40055-65. Epub 2002 Aug 8. PMID:12171933<ref>PMID:12171933</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 1m01" style="background-color:#fffaf0;"></div>

==See Also==
*[[Beta-Hexosaminidase|Beta-Hexosaminidase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Atcc 25483]]
[[Category: Beta-N-acetylhexosaminidase]]
[[Category: James, M N.G]]
[[Category: Mark, B L]]
[[Category: Vocadlo, D J]]
[[Category: Williams, S J]]
[[Category: Withers, S G]]
[[Category: Hexosaminidase]]
[[Category: Hydrolase]]
[[Category: Streptomyces plicatus]]
[[Category: Substrate assisted catalysis]]
[[Category: Tim barrel]]