title: Catalysis and sulfa drug resistance in dihydropteroate synthase.
abstract: The sulfonamide antibiotics inhibit dihydropteroate synthase (DHPS), a key enzyme in the folate pathway of bacteria and primitive eukaryotes. However, resistance mutations have severely compromised the usefulness of these drugs. We report structural, computational, and mutagenesis studies on the catalytic and resistance mechanisms of DHPS. By performing the enzyme-catalyzed reaction in crystalline DHPS, we have structurally characterized key intermediates along the reaction pathway. Results support an S(N)1 reaction mechanism via formation of a novel cationic pterin intermediate. We also show that two conserved loops generate a substructure during catalysis that creates a specific binding pocket for p-aminobenzoic acid, one of the two DHPS substrates. This substructure, together with the pterin-binding pocket, explains the roles of the conserved active-site residues and reveals how sulfonamide resistance arises.
authors.affiliation: Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
authors.forename: Mi-Kyung
authors.initials: MK
authors.lastname: Yun
authors.forename: Yinan
authors.initials: Y
authors.lastname: Wu
authors.forename: Zhenmei
authors.initials: Z
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhao
authors.forename: M Brett
authors.initials: MB
authors.lastname: Waddell
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Ferreira
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lee
authors.forename: Donald
authors.initials: D
authors.lastname: Bashford
authors.forename: Stephen W
authors.initials: SW
authors.lastname: White
mesh_terms: D010129:4-Aminobenzoic Acid / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001408:Bacillus anthracis / Q000187:drug effects / Q000201:enzymology; D055162:Biocatalysis; D020134:Catalytic Domain; D003460:Crystallization; D018360:Crystallography, X-Ray; D004094:Dihydropteroate Synthase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011756:Diphosphates / Q000737:chemistry / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D008274:Magnesium / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010226:Parabens / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D013420:Sulfamethoxazole / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000077589:Sulfathiazole; D013432:Sulfathiazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D015010:Yersinia pestis / Q000187:drug effects / Q000201:enzymology
chemical_list: D000900:Anti-Bacterial Agents; D011756:Diphosphates; D010226:Parabens; D013432:Sulfathiazoles; C107241:diphosphoric acid; D004094:Dihydropteroate Synthase; D008274:Magnesium; D013420:Sulfamethoxazole; D010129:4-Aminobenzoic Acid; D000077589:Sulfathiazole