The cytoplasmic localization and organization of the riboflavin biosynthetic enzymes in Bacillus subtilis and a possible role of the yet uncharacterized protein RibT in complex (FLAVINOSOME) formation/detoxification

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For the first time in a prokaryotic cell, the detailed localization/organization of all enzymes of a single biosynthetic pathway shall be analyzed in vivo. Exemplarily, it is planned to study the localization/organization of the enzymes RibGBAH(T) and RibC responsible for FMN/FAD biosynthesis in Bacillus subtilis. The hypothesis is that substrate channelling in an enzyme complex (“flavinosome”) allows the efficient synthesis of these cofactors. As a first step towards the characterization of a hypothetical “flavinosome” within the cytoplasm of B. subtilis the localization of the Rib-enzymes shall be investigated using cytological reporters. Furthermore, a possible interaction of the Rib-enzymes shall be determined by employing the tandem affinity purification (TAP) method. In this context the role of the B. subtilis gene ribT is of outstanding interest. This gene is located at the 3’ end of the riboflavin biosynthetic operon ribGBAHT, its biological function is still unknown. RibT possibly has N-acetyltransferase activity. Our hypothesis is, that RibT mediated acetylation of the Rib-enzymes triggers the formation of a riboflavin biosynthetic protein complex. All in all, the enzymes of the riboflavin pathway appear to be ideally suited for studying the interplay of enzymes in prokaryotic cells.