title: Characterization of a Salmonella typhimurium mutant defective in phosphoribosylpyrophosphate synthetase.
abstract: This study describes the isolation and characterization of a mutant (strain GP122) of Salmonella typhimurium with a partial deficiency of phosphoribosylpyrophosphate (PRPP) synthetase activity. This strain was isolated in a purE deoD gpt purin auxotroph by a procedure designed to select guanosine-utilizing mutants. Strain GP122 had roughly 15% of the PRPP synthetase activity and 25% of the PRPP pool of its parent strain. The mutant exhibited many of the predicted consequences of a decreased PRPP pool and a defective PRPP synthetase enzyme, including: poor growth on purine bases; decreased accumulation of 5-aminoimidazole ribonucleotide (the substrate of the blocked purE reaction) under conditions of purine starvation; excretion of anthranilic acid when grown in medium lacking tryptophan; increased resistance to inhibition by 5-fluorouracil; derepressed levels of aspartate transcarbamylase and orotate phosphoribosyltransferase, enzymes involved in the pyrimidine de novo biosynthetic pathway; growth stimulation by PRPP-sparing compounds (e.g. guanosine, histidine); poor growth in low phosphate medium; and increased heat lability of the defective enzyme. This mutant strain also had increased levels of guanosine 5'-monophosphate reductase. This genetic lesion, designated prs, was mapped by conjugation and phage P22-mediated transduction at 35 units on the Salmonella linkage map.
authors.forename: B U
authors.initials: BU
authors.lastname: Jochimsen
authors.forename: B
authors.initials: B
authors.lastname: Hove-Jensen
authors.forename: B B
authors.initials: BB
authors.lastname: Garber
authors.forename: J S
authors.initials: JS
authors.lastname: Gots
mesh_terms: D050899:GMP Reductase; D005796:Genes; D005819:Genetic Markers; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D010754:Phosphoribosyl Pyrophosphate / Q000378:metabolism; D010770:Phosphotransferases / Q000172:deficiency*; D012265:Ribonucleotides / Q000096:biosynthesis; D012268:Ribose-Phosphate Pyrophosphokinase / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D062367:ortho-Aminobenzoates / Q000096:biosynthesis
chemical_list: D005819:Genetic Markers; D009711:Nucleotides; D012265:Ribonucleotides; D062367:ortho-Aminobenzoates; C031385:anthranilic acid; C024828:aminoimidazole ribotide; D010754:Phosphoribosyl Pyrophosphate; D009247:NADH, NADPH Oxidoreductases; D050899:GMP Reductase; D010770:Phosphotransferases; D012268:Ribose-Phosphate Pyrophosphokinase