title: Structure of 3-oxoacyl-(acyl-carrier protein) synthase II from Thermus thermophilus HB8.
abstract: The beta-ketoacyl-(acyl carrier protein) synthases (beta-keto-ACP synthases; KAS) catalyse the addition of two-carbon units to the growing acyl chain during the elongation phase of fatty-acid synthesis. As key regulators of bacterial fatty-acid synthesis, they are promising targets for the development of new antibacterial agents. The crystal structure of 3-oxoacyl-ACP synthase II from Thermus thermophilus HB8 (TtKAS II) has been solved by molecular replacement and refined at 2.0 A resolution. The crystal is orthorhombic, space group P2(1)2(1)2, with unit-cell parameters a = 72.07, b = 185.57, c = 62.52 A, and contains one homodimer in the asymmetric unit. The subunits adopt the well known alpha-beta-alpha-beta-alpha thiolase fold that is common to ACP synthases. The structural and sequence similarities of TtKAS II to KAS I and KAS II enzymes of known structure from other sources support the hypothesis of comparable enzymatic activity. The dimeric state of TtKAS II is important to create each fatty-acid-binding pocket. Closer examination of KAS structures reveals that compared with other KAS structures in the apo form, the active site of TtKAS II is more accessible because of the ;open' conformation of the Phe396 side chain.
authors.affiliation: Advanced Protein Crystallography Research Group, RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan. bagautdi@spring8.or.jp
authors.forename: Bagautdin
authors.initials: B
authors.lastname: Bagautdinov
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ukita
authors.forename: Masashi
authors.initials: M
authors.lastname: Miyano
authors.forename: Naoki
authors.initials: N
authors.lastname: Kunishima
mesh_terms: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase