Mechanism of 3-Methylanthranilic Acid Derepression of the Tryptophan Operon in Escherichia coli

Document Type

Article

Language

eng

Format of Original

9 p.

Publication Date

1-1970

Publisher

American Society for Microbiology

Source Publication

Journal of Bacteriology

Source ISSN

0021-9193

Original Item ID

DOI: 10.1128/jb.101.1.209-217.1970

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.

Comments

Published version. Journal of Bacteriology, Vol. 101, No. 1 (January 1970): 209-217. DOI. © 1970 Journal of Social Psychology. Used with permission.

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