title: Structural basis for substrate binding and the catalytic mechanism of type III pantothenate kinase.
abstract: Pantothenate kinase (PanK) catalyzes the first step of the universal five-step coenzyme A (CoA) biosynthetic pathway. The recently characterized type III PanK (PanK-III, encoded by the coaX gene) is distinct in sequence, structure and enzymatic properties from both the long-known bacterial type I PanK (PanK-I, exemplified by the Escherichia coli CoaA protein) and the predominantly eukaryotic type II PanK (PanK-II). PanK-III enzymes have an unusually high Km for ATP, are resistant to feedback inhibition by CoA, and are unable to utilize the N-alkylpantothenamide family of pantothenate analogues as alternative substrates, thus making type III PanK ineffective in generating CoA analogues as antimetabolites in vivo. Previously, we reported the crystal structure of the PanK-III from Thermotoga maritima and identified it as a member of the "acetate and sugar kinase/heat shock protein 70/actin" (ASKHA) superfamily. Here we report the crystal structures of the same PanK-III in complex with one of its substrates (pantothenate), its product (phosphopantothenate) as well as a ternary complex structure of PanK-III with pantothenate and ADP. These results are combined with isothermal titration calorimetry experiments to present a detailed structural and thermodynamic characterization of the interactions between PanK-III and its substrates ATP and pantothenate. Comparison of substrate binding and catalytic sites of PanK-III with that of eukaryotic PanK-II revealed drastic differences in the binding modes for both ATP and pantothenate substrates, and suggests that these differences may be exploited in the development of new inhibitors specifically targeting PanK-III.
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Yang
authors.forename: Erick
authors.initials: E
authors.lastname: Strauss
authors.forename: Carlos
authors.initials: C
authors.lastname: Huerta
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D000266:Adenylyl Imidodiphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D001665:Binding Sites; D002151:Calorimetry; D002384:Catalysis; D003460:Crystallization; D016480:Helicobacter pylori / Q000201:enzymology; D007700:Kinetics; D008969:Molecular Sequence Data; D010205:Pantothenic Acid / Q000737:chemistry; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000378:metabolism*; D013816:Thermodynamics; D020124:Thermotoga maritima / Q000201:enzymology
chemical_list: D010205:Pantothenic Acid; D000266:Adenylyl Imidodiphosphate; D000244:Adenosine Diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C023088:pantothenate kinase