[Riboflavin biosynthesis operon of Bacillus subtilis. XIV. Operator-constitutive mutants]

Numerous operator-constitutive mutants of riboflavin biosynthesis were selected. All of them map in a short region of the Bacillus subtilis chromosome. The yield of riboflavin synthetase from this mutant is different, but in most cases much lower than the maximal yield from a repressor minus strain. Our tentative explanation is a partial overlap of the sites for the adsorption of repressor and RNA-polymerase. Therefore the affinity to the transcribing enzyme is diminished in the operator constitutive strains. The affinity of the repressor-effector complex to the operator depends on the effector structure.