title: Peroxisomal plant 3-ketoacyl-CoA thiolase structure and activity are regulated by a sensitive redox switch.
abstract: The breakdown of fatty acids, performed by the beta-oxidation cycle, is crucial for plant germination and sustainability. beta-Oxidation involves four enzymatic reactions. The final step, in which a two-carbon unit is cleaved from the fatty acid, is performed by a 3-ketoacyl-CoA thiolase (KAT). The shortened fatty acid may then pass through the cycle again (until reaching acetoacetyl-CoA) or be directed to a different cellular function. Crystal structures of KAT from Arabidopsis thaliana and Helianthus annuus have been solved to 1.5 and 1.8 A resolution, respectively. Their dimeric structures are very similar and exhibit a typical thiolase-like fold; dimer formation and active site conformation appear in an open, active, reduced state. Using an interdisciplinary approach, we confirmed the potential of plant KATs to be regulated by the redox environment in the peroxisome within a physiological range. In addition, co-immunoprecipitation studies suggest an interaction between KAT and the multifunctional protein that is responsible for the preceding two steps in beta-oxidation, which would allow a route for substrate channeling. We suggest a model for this complex based on the bacterial system.
authors.affiliation: Protein Chemistry Group, Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark. vpye@tcd.ie
authors.forename: Valerie E
authors.initials: VE
authors.lastname: Pye
authors.forename: Caspar E
authors.initials: CE
authors.lastname: Christensen
authors.forename: James H
authors.initials: JH
authors.lastname: Dyer
authors.forename: Susan
authors.initials: S
authors.lastname: Arent
authors.forename: Anette
authors.initials: A
authors.lastname: Henriksen
mesh_terms: D000102:Acetyl-CoA C-Acyltransferase / Q000737:chemistry*; D017360:Arabidopsis / Q000201:enzymology*; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D005227:Fatty Acids / Q000737:chemistry; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006368:Helianthus / Q000201:enzymology*; D008055:Lipids / Q000737:chemistry; D008954:Models, Biological; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D020675:Peroxisomes / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D005227:Fatty Acids; D008055:Lipids; D000102:Acetyl-CoA C-Acyltransferase; D010100:Oxygen
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