1m01: Difference between revisions

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    <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>
+     <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.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==
@@ Line 25: / Line 34: @@
 *[[Beta-Hexosaminidase 3D structures|Beta-Hexosaminidase 3D structures]]
 *[[Beta-N-acetylhexosaminidase 3D structures|Beta-N-acetylhexosaminidase 3D structures]]
+== References ==
+<references/>
 __TOC__
 </StructureSection>