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Mutant Strains of Escherichia coli K-12 Exhibiting Enhanced Sensitivity to 5-Methyltryptophan¹

^a Department of Biochemistry, Purdue University, Lafayette, Indiana 47907

ABSTRACT

Eighteen mutants (designated MT^s), isolated in Escherichia coli K-12, showed increased sensitivity to inhibition of growth by 5-methyltryptophan. All mutants were also much more sensitive to 4-methyltryptophan and 7-azatryptophan but exhibited near normal sensitivity to 5-fluorotryptophan and 6-fluorotryptophan. All of the mutations were linked to the trp operon. Their locations within the trp operon were established by deletion mapping. There was good agreement between the map position of an MT^s mutation and a lowered activity of one of the tryptophan pathway enzymes. Three mutants, one of which contained a mutation that mapped within the trpE gene, were deficient in their ability to use glutamine as an amino donor in the formation of anthranilic acid. Another trpE mutation led to the production of an anthranilate synthetase with an increased sensitivity to feedback inhibition by tryptophan.

² Present address: University of the Negev, Beer-Sheva, Israel.

¹ This is Journal Paper no. 4730 of the Purdue Agricultural Experiment Station.