View source for 1xpl

[[Image:1xpl.gif|left|200px]]<br /><applet load="1xpl" size="450" color="white" frame="true" align="right" spinBox="true" 
caption="1xpl, resolution 2.&Aring;" />
'''Crystal Structure of Staphylococcus aureus HMG-COA Synthase with Acetoacetyl-COA and Acetylated Cysteine'''<br />

==Overview==
The formation of carbon-carbon bonds via an acyl-enzyme intermediate plays, a central role in fatty acid, polyketide, and isoprenoid biosynthesis., Uniquely among condensing enzymes, 3-hydroxy-3-methylglutaryl (HMG)-CoA, synthase (HMGS) catalyzes the formation of a carbon-carbon bond by, activating the methyl group of an acetylated cysteine. This reaction is, essential in Gram-positive bacteria, and represents the first committed, step in human cholesterol biosynthesis. Reaction kinetics, isotope, exchange, and mass spectroscopy suggest surprisingly that HMGS is able to, catalyze the "backwards" reaction in solution, where HMG-CoA is cleaved to, form acetoacetyl-CoA (AcAc-CoA) and acetate. Here, we trap a complex of, acetylated HMGS from Staphylococcus aureus and bound acetoacetyl-CoA by, cryo-cooling enzyme crystals at three different times during the course of, its back-reaction with its physiological product (HMG-CoA). This, nonphysiological "backwards" reaction is used to understand the details of, the physiological reaction with regards to individual residues involved in, catalysis and substrate/product binding. The structures suggest that an, active-site glutamic acid (Glu-79) acts as a general base both in the, condensation between acetoacetyl-CoA and the acetylated enzyme, and the, hydrolytic release of HMG-CoA from the enzyme. The ability to trap this, enzyme-intermediate complex may suggest a role for protein dynamics and, the interplay between protomers during the normal course of catalysis.

==About this Structure==
1XPL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Staphylococcus_aureus_subsp._aureus Staphylococcus aureus subsp. aureus] with SO4 and CAA as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Hydroxymethylglutaryl-CoA_synthase Hydroxymethylglutaryl-CoA synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.3.10 2.3.3.10] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1XPL OCA]. 

==Reference==
3-hydroxy-3-methylglutaryl-CoA synthase intermediate complex observed in "real-time"., Theisen MJ, Misra I, Saadat D, Campobasso N, Miziorko HM, Harrison DH, Proc Natl Acad Sci U S A. 2004 Nov 23;101(47):16442-7. Epub 2004 Oct 21. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=15498869 15498869]
[[Category: Hydroxymethylglutaryl-CoA synthase]]
[[Category: Single protein]]
[[Category: Staphylococcus aureus subsp. aureus]]
[[Category: Campobasso, N.]]
[[Category: Harrison, D.H.T.]]
[[Category: Misra, I.]]
[[Category: Miziorko, H.M.]]
[[Category: Saadat, D.]]
[[Category: Theisen, M.J.]]
[[Category: CAA]]
[[Category: SO4]]
[[Category: cholesterol biosynthesis]]
[[Category: coenzyme a]]
[[Category: condensing enzyme]]
[[Category: hmg-coa synthase]]
[[Category: hmgs]]
[[Category: thiolase fold]]

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