tyrR, A Regulatory Gene of Tyrosine Biosynthesis in Salmonella typhimurium

Abstract

4-Fluorophenylalanine-resistant mutants of Salmonella typhimurium were isolated in which tyrosine pathway enzymes were not repressed by L-tyrosine. The mutants produced elevated levels of 3-deoxy-D-arabinoheptulosonic acid 7-phosphate (DAHP) synthetase (tyr) and chorismate mutase T-prephenate dehydrogenase, and these enzymes as well as transaminase A were not repressed by high concentrations of tyrosine. Genetic analysis revealed that a mutation in a gene designated tyrR was responsible for the constitutivity of the tyrosine pathway enzymes in strains SG1, SG7, and SG9, and that tyrR was linked to pyrF. In strain SG1 a mutation had also occurred in aroF, the structural gene for DAHP synthetase (tyr), resulting in loss of sensitivity of this enzyme to end-product inhibition. There appeared to be no relationship between loss of feedback inhibition and loss of end-product repression, since derivative strains of SG1 that carried only the tyrR mutation behaved like the singly mutated tyrR strains, SG7 and SG9, in showing high constitutive levels of tyrosine-specific enzymes that were not repressed by tyrosine.Sanderson; SC19, a Salmonella-Escherichia coli hybrid, was provided by J. S. Gots; tyrA3, tyrA33, pheA3, and trpA52 were provided by Y. Nishioka; and pyrF146 was provided by D. Berkowitz. B. Low provided E. coli episomal strains KLF23/KL181 and F152/KL253. Strain SG1 was isolated from an 8 mM 4-fluorophenylalanine plate which was inoculated with a transduction mixture containing tyrA33 cells and a phage P22 lysate from strain SG11 (a tyrO mutant 1094 on July 31, 2020 by guest

Properties of tyrosine-inhibitable 3-deoxy-d-arabinoheptulosonic acid-7-phosphate synthase from Salmonella

“…In wild-type Salmonella, tyrosine-inhibitable DAHP synthase accounts for approximately 10% of total DAHP synthase activity (11). In the operator-constitutive mutant SG12 grown at 250C (13), activity of DAHP synthase is twice as high as found at 37°C (10), and activity of DAHP synthase (tyr) is 85% of the total ( Table 1). The levels obtained were about 35-fold higher than in wild-type cells grown in minimal medium and approximated those of DAHP synthase (phe) found by Simpson et al (23) structural gene for the phenylalanine isoenzyme into the genome of specialized transducing phage lambda.…”

Cyclic AMP Receptor Protein and TyrR Are Required for Acid pH and Anaerobic Induction of hyaB and aniC in Salmonella typhimurium

“…The results shown in Fig. 1C indicated that this gene is the S. typhimurium homolog of tyrR (90% identity over 30 amino acids), a regulator of aromatic amino acid biosynthesis and transport (15,26).…”

Linkage map of Salmonella typhimurium, edition IV.

“…Some of the thiE, F mutants mapped in this general region (Gots, personal communication) may be homologous to thiB. A single transducing fragment carries phe and tyr (213), as well as aroF and tyrO (formerly fpr) (109). The gene pyrG is jointly transduced with cysCD (25).…”