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[[Image:2sqc.jpg|left|200px]]
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{{STRUCTURE_2sqc|  PDB=2sqc  |  SCENE=  }}
'''SQUALENE-HOPENE CYCLASE FROM ALICYCLOBACILLUS ACIDOCALDARIUS'''


==SQUALENE-HOPENE CYCLASE FROM ALICYCLOBACILLUS ACIDOCALDARIUS==
<StructureSection load='2sqc' size='340' side='right'caption='[[2sqc]], [[Resolution|resolution]] 2.00&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2sqc]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Alicyclobacillus_acidocaldarius Alicyclobacillus acidocaldarius]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2SQC OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2SQC FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=C8E:(HYDROXYETHYLOXY)TRI(ETHYLOXY)OCTANE'>C8E</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2sqc FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2sqc OCA], [https://pdbe.org/2sqc PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2sqc RCSB], [https://www.ebi.ac.uk/pdbsum/2sqc PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2sqc ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SQHC_ALIAD SQHC_ALIAD] Catalyzes the cyclization of squalene into hopene.
== 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/sq/2sqc_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=2sqc ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Squalene cyclases catalyze a cationic cyclization cascade, which is homologous to a key step in cholesterol biosynthesis. The structure of the enzyme from Alicyclobacillus acidocaldarius has been determined in a new crystal form at 2.0 A resolution (1 A=0.1 nm) and refined to an R-factor of 15.3 % (Rfree=18.7 %). The structure indicates how the initial protonation and the final deprotonation of squalene occur and how the transient carbocations are stabilized. The pathways of the flexible educt squalene from the membrane interior to the active center cavity and of the rigid fused-ring product hopene in the reverse direction are discussed. The enzyme contains eight so-called QW-sequence repeats that fortify the alpha/alpha-barrels by an intricate interaction network. They are unique to the known triterpene cyclases and are presumed to shield these enzymes against the released enthalpy of the highly exergonic catalyzed reaction. The enzyme is a monotopic membrane protein, the membrane-binding interactions of which are described and compared with those of two prostaglandin-H2 synthase isoenzymes, the only other structurally characterized proteins of this type. In the crystals the membrane-binding regions face each other, suggesting a micelle-type detergent structure between them.


==Overview==
The structure of the membrane protein squalene-hopene cyclase at 2.0 A resolution.,Wendt KU, Lenhart A, Schulz GE J Mol Biol. 1999 Feb 12;286(1):175-87. PMID:9931258<ref>PMID:9931258</ref>
Squalene cyclases catalyze a cationic cyclization cascade, which is homologous to a key step in cholesterol biosynthesis. The structure of the enzyme from Alicyclobacillus acidocaldarius has been determined in a new crystal form at 2.0 A resolution (1 A=0.1 nm) and refined to an R-factor of 15.3 % (Rfree=18.7 %). The structure indicates how the initial protonation and the final deprotonation of squalene occur and how the transient carbocations are stabilized. The pathways of the flexible educt squalene from the membrane interior to the active center cavity and of the rigid fused-ring product hopene in the reverse direction are discussed. The enzyme contains eight so-called QW-sequence repeats that fortify the alpha/alpha-barrels by an intricate interaction network. They are unique to the known triterpene cyclases and are presumed to shield these enzymes against the released enthalpy of the highly exergonic catalyzed reaction. The enzyme is a monotopic membrane protein, the membrane-binding interactions of which are described and compared with those of two prostaglandin-H2 synthase isoenzymes, the only other structurally characterized proteins of this type. In the crystals the membrane-binding regions face each other, suggesting a micelle-type detergent structure between them.


==About this Structure==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
2SQC is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Alicyclobacillus_acidocaldarius Alicyclobacillus acidocaldarius]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2SQC OCA].
</div>
<div class="pdbe-citations 2sqc" style="background-color:#fffaf0;"></div>


==Reference==
==See Also==
The structure of the membrane protein squalene-hopene cyclase at 2.0 A resolution., Wendt KU, Lenhart A, Schulz GE, J Mol Biol. 1999 Feb 12;286(1):175-87. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/9931258 9931258]
*[[Squalene-hopene cyclase|Squalene-hopene cyclase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Alicyclobacillus acidocaldarius]]
[[Category: Alicyclobacillus acidocaldarius]]
[[Category: Single protein]]
[[Category: Large Structures]]
[[Category: Schulz, G E.]]
[[Category: Schulz GE]]
[[Category: Wendt, K U.]]
[[Category: Wendt KU]]
[[Category: Cholesterol biosynthesis]]
[[Category: Isomerase]]
[[Category: Monotopic membrane protein]]
[[Category: Qw-sequence]]
[[Category: Repeat]]
[[Category: Triterpene cyclase]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May  4 17:21:21 2008''

Latest revision as of 06:46, 9 August 2023

SQUALENE-HOPENE CYCLASE FROM ALICYCLOBACILLUS ACIDOCALDARIUS

2sqc, resolution 2.00Å

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