title: The crystal structure of human mitochondrial 3-ketoacyl-CoA thiolase (T1): insight into the reaction mechanism of its thiolase and thioesterase activities.
abstract: Crystal structures of human mitochondrial 3-ketoacyl-CoA thiolase (hT1) in the apo form and in complex with CoA have been determined at 2.0 Å resolution. The structures confirm the tetrameric quaternary structure of this degradative thiolase. The active site is surprisingly similar to the active site of the Zoogloea ramigera biosynthetic tetrameric thiolase (PDB entries 1dm3 and 1m1o) and different from the active site of the peroxisomal dimeric degradative thiolase (PDB entries 1afw and 2iik). A cavity analysis suggests a mode of binding for the fatty-acyl tail in a tunnel lined by the Nβ2-Nα2 loop of the adjacent subunit and the Lα1 helix of the loop domain. Soaking of the apo hT1 crystals with octanoyl-CoA resulted in a crystal structure in complex with CoA owing to the intrinsic acyl-CoA thioesterase activity of hT1. Solution studies confirm that hT1 has low acyl-CoA thioesterase activity for fatty acyl-CoA substrates. The fastest rate is observed for the hydrolysis of butyryl-CoA. It is also shown that T1 has significant biosynthetic thiolase activity, which is predicted to be of physiological importance.
authors.affiliation: Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland.
authors.forename: Tiila Riikka
authors.initials: TR
authors.lastname: Kiema
authors.affiliation: Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland.
authors.forename: Rajesh K
authors.initials: RK
authors.lastname: Harijan
authors.affiliation: Karolinska Institutet, Department of Laboratory Medicine, Division of Clinical Chemistry, Karolinska University Hospital, SE-141 86 Stockholm, Sweden.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Strozyk
authors.affiliation: Department of Pediatrics, Graduate School of Medicine, Gifu University, Yanagido 1-1, Gifu 501-1194, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Fukao
authors.affiliation: Karolinska Institutet, Department of Laboratory Medicine, Division of Clinical Chemistry, Karolinska University Hospital, SE-141 86 Stockholm, Sweden.
authors.forename: Stefan E H
authors.initials: SE
authors.lastname: Alexson
authors.affiliation: Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland.
authors.forename: Rik K
authors.initials: RK
authors.lastname: Wierenga
mesh_terms: D000102:Acetyl-CoA C-Acyltransferase / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D003065:Coenzyme A / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D008928:Mitochondria / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D013869:Thiolester Hydrolases / Q000737:chemistry / Q000378:metabolism; D015045:Zoogloea / Q000201:enzymology
chemical_list: D000102:Acetyl-CoA C-Acyltransferase; D013869:Thiolester Hydrolases; D003065:Coenzyme A
keywords: coenzyme A; lipid metabolism; oxyanion hole; thioester chemistry