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'''Crystal Structure of Staphylococcus aureus HMG-COA Synthase with HMG-CoA and Acetoacetyl-COA and Acetylated Cysteine''' | '''Crystal Structure of Staphylococcus aureus HMG-COA Synthase with HMG-CoA and Acetoacetyl-COA and Acetylated Cysteine''' | ||
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[[Category: Saadat, D.]] | [[Category: Saadat, D.]] | ||
[[Category: Theisen, M J.]] | [[Category: Theisen, M J.]] | ||
[[Category: | [[Category: Cholesterol biosynthesis]] | ||
[[Category: | [[Category: Coenzyme some]] | ||
[[Category: | [[Category: Condensing enzyme]] | ||
[[Category: | [[Category: Hmg-coa synthase]] | ||
[[Category: | [[Category: Hmg]] | ||
[[Category: | [[Category: Thiolase fold]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 15:20:16 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 15:20, 3 May 2008
Crystal Structure of Staphylococcus aureus HMG-COA Synthase with HMG-CoA and Acetoacetyl-COA and Acetylated Cysteine
OverviewOverview
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 StructureAbout this Structure
1XPM is a Single protein structure of sequence from Staphylococcus aureus subsp. aureus. Full crystallographic information is available from OCA.
ReferenceReference
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:15498869 Page seeded by OCA on Sat May 3 15:20:16 2008