Relationship between the secondary structure and the regulatory activity of the leader region of the riboflavin biosynthesis operon in Bacillus subtilis

Abstract

Insertion and deletion mutagenesis of the leader region of the Bacillus subtilis rib operon encoding FMN-specific sensor RNA was conducted. Insertions of different structure and length in the conservative motif of the leader sequence (Rfn-element) were shown to cause partially constitutive expression of the operon resulted in an increased accumulation of riboflavin. At the same time, introducing into the genome of insertion mutants an additional ribC mutation blocking FMN synthesis leads to an increase in riboflavin production. Deletion of the main Rho-dependent transcription terminator gives rise to the same effect. These results indicate that some additional FMN-dependent regulation is involved in rib-operon control, which is, however, still connected with the primary and secondary structure of the leader region.