title: Ligand-induced conformational changes within a hexameric Acyl-CoA thioesterase.
abstract: Acyl-coenzyme A (acyl-CoA) thioesterases play a crucial role in the metabolism of activated fatty acids, coenzyme A, and other metabolic precursor molecules including arachidonic acid and palmitic acid. These enzymes hydrolyze coenzyme A from acyl-CoA esters to mediate a range of cellular functions including β-oxidation, lipid biosynthesis, and signal transduction. Here, we present the crystal structure of a hexameric hot-dog domain-containing acyl-CoA thioesterase from Bacillus halodurans in the apo-form and provide structural and comparative analyses to the coenzyme A-bound form to identify key conformational changes induced upon ligand binding. We observed dramatic ligand-induced changes at both the hot-dog dimer and the trimer-of-dimer interfaces; the dimer interfaces in the apo-structure differ by over 20% and decrease to about half the size in the ligand-bound state. We also assessed the specificity of the enzyme against a range of fatty acyl-CoA substrates and have identified a preference for short-chain fatty acyl-CoAs. Coenzyme A was shown both to negatively regulate enzyme activity, representing a direct inhibitory feedback, and consistent with the structural data, to destabilize the quaternary structure of the enzyme. Coenzyme A-induced conformational changes in the C-terminal helices of enzyme were assessed through mutational analysis and shown to play a role in regulating enzyme activity. The conformational changes are likely to be conserved from bacteria through to humans and provide a greater understanding, particularly at a structural level, of thioesterase function and regulation.
authors.affiliation: School of Chemistry and Molecular Biosciences and Australian Infectious Disease Research Centre, University of Queensland, Brisbane, Queensland 4072.
authors.forename: Mary
authors.initials: M
authors.lastname: Marfori
authors.affiliation: School of Chemistry and Molecular Biosciences and Australian Infectious Disease Research Centre, University of Queensland, Brisbane, Queensland 4072; Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072. Electronic address: b.kobe@uq.edu.au.
authors.forename: Bostjan
authors.initials: B
authors.lastname: Kobe
authors.affiliation: School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, New South Wales 2650, Australia. Electronic address: jforwood@csu.edu.au.
authors.forename: Jade K
authors.initials: JK
authors.lastname: Forwood
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D003065:Coenzyme A / Q000737:chemistry* / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008024:Ligands; D010170:Palmitoyl-CoA Hydrolase / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D008024:Ligands; D010170:Palmitoyl-CoA Hydrolase; D003065:Coenzyme A