PMID:4904235

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Citation

Held, WA and Smith, OH (1970) Mechanism of 3-methylanthranilic acid derepression of the tryptophan operon in Escherichia coli. J. Bacteriol. 101:209-17

Abstract

3-Methylanthranilic acid (3MA) inhibits growth and causes derepression of the tryptophan biosynthetic enzymes in wild-type strains of Escherichia coli. Previous reports attributed this effect to an inhibition of the conversion of 1-(o-carboxyphenylamino)-1-deoxyribulose 5-phosphate to indole-3-glycerol phosphate and a consequent reduction in the concentration of endogenous tryptophan. Our studies have shown that 3MA-resistant mutants linked to the tryptophan operon have a feedback-resistant anthranilate synthetase; mutants with an altered indole-3-glycerol phosphate synthetase were not found. 3MA or 7-methylindole can be metabolized to 7-methyltryptophan, and 3MA, 7-methylindole, and 7-methyltryptophan lead to derepression of the tryptophan operon. Furthermore, 3MA-resistant mutants are also resistant to 7-methylindole derepression. These results strongly suggest that the primary cause of derepression by 3MA is through its conversion to 7-methyltryptophan, which can inhibit anthranilate synthetase, thereby decreasing the concentration of endogenous tryptophan. Unlike 5- or 6-methyltryptophan, 7-methyltryptophan does not appear to function as an active corepressor.

Links

PubMed PMC250472

Keywords

Anthranilic Acids/analysis; Anthranilic Acids/metabolism; Culture Media; Enzyme Repression/drug effects; Escherichia coli/enzymology; Escherichia coli/growth & development; Glycerol/metabolism; Indoles/metabolism; Kinetics; Ligases; Molecular Biology; Mutation; Operon; Pentoses/metabolism; Phosphates/metabolism; Tritium; Tryptophan/biosynthesis; Tryptophan/metabolism

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Materials and Methods Used

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Phenotype Annotations

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Phenotype of Taxon Information Genotype Information (if known) Condition Information OMP ID OMP Term Name ECO ID ECO Term Name Notes Status

a mutation or genetic difference within a strain

  • Taxon: Escherichia coli
  • Strain: K-12
  • Substrain: W1485 tna
  • NCBI Taxon ID: 83333
  • Genotype of Reference Strain: trpE+
  • Genotype of Experimental Strain : trpEFBR 2-50
  • Reference Condition:

Mutation to the trpE gene conferred resistance toward anthranilate synthetase. This was also seen in strain trpEFBR1-42. See Table 1.

a mutation or genetic difference within a strain

  • Taxon: Escherichia coli
  • Strain: K-12
  • Substrain: W1485 tna
  • NCBI Taxon ID: 83333
  • Genotype of Reference Strain: trpE+
  • Genotype of Experimental Strain : MAR mutation in trpE gene.
  • Reference Condition:

MAR mutation to the trpE gene conferred resistance toward anthranilate synthetase in MAR 13. This was also seen in strains MAR 1-9, MAR 31' and MAR 22. See Table 1.

a mutation or genetic difference within a strain

  • Taxon: Escherichia coli
  • Strain: K-12
  • Substrain: W1485 tna
  • NCBI Taxon ID: 83333
  • Genotype of Reference Strain: trpE+ - trpR+
  • Genotype of Experimental Strain : trpR trpEFBR44
  • Reference Condition:

The trpR mutation and trpEFBR double mutations conferred resistance toward anthranilate synthetase mutants. This was seen in strains trpR-trpEFBR46 See table 1.


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