View source for 1sci


==K236L mutant of hydroxynitrile lyase from Hevea brasiliensis==
<StructureSection load='1sci' size='340' side='right'caption='[[1sci]], [[Resolution|resolution]] 2.18&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1sci]] is a 1 chain structure with sequence from [http://en.wikipedia.org/wiki/Hevbr Hevbr]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SCI OCA]. For a <b>guided tour on the structure components</b> use [http://proteopedia.org/fgij/fg.htm?mol=1SCI FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><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"><div style='overflow: auto; max-height: 3em;'>[[1qj4|1qj4]], [[1yas|1yas]], [[2yas|2yas]], [[3yas|3yas]], [[4yas|4yas]], [[5yas|5yas]], [[6yas|6yas]], [[7yas|7yas]], [[1sc9|1sc9]], [[1sck|1sck]], [[1scq|1scq]]</div></td></tr>
<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">HNL ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=3981 HEVBR])</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Lyase Lyase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.2.46 and 4.1.2.47 4.1.2.46 and 4.1.2.47] </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=1sci FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1sci OCA], [http://pdbe.org/1sci PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1sci RCSB], [http://www.ebi.ac.uk/pdbsum/1sci PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1sci ProSAT]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/HNL_HEVBR HNL_HEVBR]] Involved in cyanogenesis, the release of HCN from injured tissues. Decomposes a varieties of (R) or (S) cyanohydrins into HCN and the corresponding aldehydes and ketones. The natural substrate of this enzyme is (S)-acetone cyanohydrin. 
== 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/sc/1sci_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=1sci ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The hydroxynitrile lyases (HNLs) from Hevea brasiliensis (HbHNL) and from Manihot esculenta (MeHNL) are both members of the alpha/beta-hydrolase superfamily. Mechanistic proposals have been put forward in the past for both enzymes; they differed with respect to the role of the active-site lysine residue for which a catalytic function was claimed for the Hevea enzyme but denied for the Manihot enzyme. We applied a freeze-quench method to prepare crystals of the complex of HbHNL with the biological substrate acetone cyanohydrin and determined its three-dimensional structure. Site-directed mutagenesis was used to prepare the mutant K236L, which is inactive although its three-dimensional structure is similar to the wild-type enzyme. However, the structure of the K236L-acetone cyanohydrin complex shows the substrate in a different orientation from the wild-type complex. Finite difference Poisson-Boltzmann calculations show that in the absence of Lys(236) the catalytic base His(235) would be protonated at neutral pH. All of this suggests that Lys(236) is instrumental for catalysis in several ways, i.e. by correctly positioning the substrate, by stabilizing the negatively charged reaction product CN(-), and by modulating the basicity of the catalytic base. These data complete the elucidation of the reaction mechanism of alpha/beta-hydrolase HNLs, in which the catalytic triad acts as a general base rather than as a nucleophile; proton abstraction from the substrate is performed by the serine, and reprotonation of the product cyanide is performed by the histidine residues. Together with a threonine side chain, the active-site serine and lysine are also involved in substrate binding.

Reaction mechanism of hydroxynitrile lyases of the alpha/beta-hydrolase superfamily: the three-dimensional structure of the transient enzyme-substrate complex certifies the crucial role of LYS236.,Gruber K, Gartler G, Krammer B, Schwab H, Kratky C J Biol Chem. 2004 May 7;279(19):20501-10. Epub 2004 Mar 3. PMID:14998991<ref>PMID:14998991</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 1sci" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Hevbr]]
[[Category: Large Structures]]
[[Category: Lyase]]
[[Category: Gartler, G]]
[[Category: Gruber, K]]
[[Category: Krammer, B]]
[[Category: Kratky, C]]
[[Category: Schwab, H]]
[[Category: Alpha-beta hydrolase fold]]
[[Category: Catalytic triad]]