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==SQUALENE-HOPENE CYCLASE== | |||
<StructureSection load='3sqc' size='340' side='right'caption='[[3sqc]], [[Resolution|resolution]] 2.80Å' scene=''> | |||
== Structural highlights == | |||
<table><tr><td colspan='2'>[[3sqc]] is a 3 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=3SQC OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3SQC 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]] 2.8Å</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=3sqc FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3sqc OCA], [https://pdbe.org/3sqc PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3sqc RCSB], [https://www.ebi.ac.uk/pdbsum/3sqc PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3sqc 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/3sqc_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=3sqc 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. | |||
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> | |||
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br> | |||
</div> | |||
<div class="pdbe-citations 3sqc" style="background-color:#fffaf0;"></div> | |||
== | ==See Also== | ||
Squalene | *[[Squalene-hopene cyclase|Squalene-hopene cyclase]] | ||
== References == | |||
== | <references/> | ||
__TOC__ | |||
</StructureSection> | |||
[[Category: Alicyclobacillus acidocaldarius]] | [[Category: Alicyclobacillus acidocaldarius]] | ||
[[Category: | [[Category: Large Structures]] | ||
[[Category: Schulz | [[Category: Schulz GE]] | ||
[[Category: Wendt | [[Category: Wendt KU]] | ||
Latest revision as of 09:49, 9 August 2023
SQUALENE-HOPENE CYCLASESQUALENE-HOPENE CYCLASE
Structural highlights
FunctionSQHC_ALIAD Catalyzes the cyclization of squalene into hopene. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSqualene 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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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