title: The crystal structure of a plant 3-ketoacyl-CoA thiolase reveals the potential for redox control of peroxisomal fatty acid beta-oxidation.
abstract: Crystal structures of peroxisomal Arabidopsis thaliana 3-ketoacyl-CoA thiolase (AtKAT), an enzyme of fatty acid beta-oxidation, are reported. The subunit, a typical thiolase, is a combination of two similar alpha/beta domains capped with a loop domain. The comparison of AtKAT with the Saccharomyces cerevisiae homologue (ScKAT) structure reveals a different placement of subunits within the functional dimers and that a polypeptide segment forming an extended loop around the open catalytic pocket of ScKAT converts to alpha-helix in AtKAT, and occludes the active site. A disulfide is formed between Cys192, on this helix, and Cys138, a catalytic residue. Access to Cys138 is determined by the structure of this polypeptide segment. AtKAT represents an oxidized, previously unknown inactive form, whilst ScKAT is the reduced and active enzyme. A high level of sequence conservation is observed, including Cys192, in eukaryotic peroxisomal, but not mitochondrial or prokaryotic KAT sequences, for this labile loop/helix segment. This indicates that KAT activity in peroxisomes is influenced by a disulfide/dithiol change linking fatty acid beta-oxidation with redox regulation.
authors.affiliation: Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
authors.forename: Ramasubramanian
authors.initials: R
authors.lastname: Sundaramoorthy
authors.forename: Elena
authors.initials: E
authors.lastname: Micossi
authors.forename: Magnus S
authors.initials: MS
authors.lastname: Alphey
authors.forename: Véronique
authors.initials: V
authors.lastname: Germain
authors.forename: James H
authors.initials: JH
authors.lastname: Bryce
authors.forename: Steve M
authors.initials: SM
authors.lastname: Smith
authors.forename: Gordon A
authors.initials: GA
authors.lastname: Leonard
authors.forename: William N
authors.initials: WN
authors.lastname: Hunter
mesh_terms: D000102:Acetyl-CoA C-Acyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D005227:Fatty Acids / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D005227:Fatty Acids; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D000102:Acetyl-CoA C-Acyltransferase