PMID:4904235
| 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 |
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| 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. |
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| 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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a mutation or genetic difference within a strain |
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