title: Leaky pantothenate and thiamin mutations of Salmonella typhimurium conferring suphometuron methyl sensitivity.
abstract: The herbicide suphometuron methyl inhibits the utilization of pyruvate and 2-ketobutyrate by the branched-chain amino acid biosynthetic enzyme acetolactate synthase. Eighteen insertions of the transposon Tn10 into the genome of Salmonella typhimurium LT2 caused hypersensitivity to this herbicide. Five of these insertions conferred a partial auxotrophic requirement. Concurrent herbicide sensitivity and heat-labile pantothenate auxotrophy was due to panD::Tn10 mutations, while coincident sulphometuron methyl sensitivity and thiamin auxotrophy was attributable to thiA::Tn10 mutations. The phenotypes of these mutations suggested that coenzyme A and thiamin pyrophosphate availability modulated the cells' response to sulphometuron methyl. A model suggesting a key role for 2-ketobutyrate accumulation in herbicide action is supported by the function of thiamin pyrophosphate in 2-ketoacid metabolism and the known role of a 2-ketoacid in coenzyme A synthesis.
authors.affiliation: Central Research and Development Department, E. I. du Pont de Nemours and Company, Wilmington, DE 19880-0328.
authors.forename: R A
authors.initials: RA
authors.lastname: LaRossa
authors.forename: T K
authors.initials: TK
authors.lastname: Van Dyk
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors*; D000483:Alleles; D001426:Bacterial Proteins / Q000096:biosynthesis; D002087:Butyrates / Q000378:metabolism; D009154:Mutation; D007652:Oxo-Acid-Lyases / Q000037:antagonists & inhibitors*; D010205:Pantothenic Acid / Q000378:metabolism*; D010641:Phenotype; D011773:Pyruvates / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics*; D013453:Sulfonylurea Compounds / Q000494:pharmacology*; D013489:Suppression, Genetic; D013831:Thiamine / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002087:Butyrates; D011773:Pyruvates; D013453:Sulfonylurea Compounds; D010205:Pantothenic Acid; C005087:alpha-ketobutyric acid; D000095:Acetolactate Synthase; D007652:Oxo-Acid-Lyases; C042031:sulfometuron methyl; D013831:Thiamine