Beschreibung:
<jats:p><jats:styled-content style="fixed-case">FMN</jats:styled-content> riboswitches are genetic elements that, in many bacteria, control genes responsible for biosynthesis and/or transport of riboflavin (vitamin B<jats:sub>2</jats:sub>). We report that the <jats:italic>Escherichia coli ribB</jats:italic> <jats:styled-content style="fixed-case">FMN</jats:styled-content> riboswitch controls expression of the essential gene <jats:italic>ribB</jats:italic> coding for the riboflavin biosynthetic enzyme 3,4‐dihydroxy‐2‐butanone‐4‐phosphate synthase (RibB; <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.chem.qmul.ac.uk/iubmb/enzyme/EC4/1/99/12.html">EC 4.1.99.12</jats:ext-link>). Our data show that the <jats:italic>E. coli ribB</jats:italic> <jats:styled-content style="fixed-case">FMN</jats:styled-content> riboswitch is unusual because it operates at the transcriptional and also at the translational level. Expression of <jats:italic>ribB</jats:italic> is negatively affected by <jats:styled-content style="fixed-case">FMN</jats:styled-content> and by the <jats:styled-content style="fixed-case">FMN</jats:styled-content> analog roseoflavin mononucleotide, which is synthesized enzymatically from roseoflavin and <jats:styled-content style="fixed-case">ATP</jats:styled-content>. Consequently, in addition to flavoenzymes, the <jats:italic>E. coli ribB</jats:italic> <jats:styled-content style="fixed-case">FMN</jats:styled-content> riboswitch constitutes a target for the antibiotic roseoflavin produced by <jats:italic>Streptomyces davawensis</jats:italic>.</jats:p>