A mutation affecting the valine sensitivity of the acetohydroxyacid synthase III isoenzyme in E. coli K-12

The ilv-751 mutation (obtained by mu phage mediated mutagenesis) affects the sensitivity to valine inhibition of the acetohydroxy acid synthase III isoenzyme of E. coli K-12, as shown by constructing multiple mutants containing the ilv-751 mutation and only one of the genes for the expression of the three acetohydroxy acid synthase isoenzymes, at once. The mutation is dominant. This suggests that the phenotype of ilv-751 mutation is not caused by inactivation of a gene concerned with the expression of the AHASIII enzyme, consequent to prophage insertion into that locus. © 1981.