Flavin mononucleotide riboswitch (FMN riboswitch)

The Flavin mononucleotide (FMN) riboswitch, also known as the RFN element, is a highly conserved regulatory RNA element found in the 5' untranslated regions of bacterial messenger RNAs (Winkler et al., 2002). It functions as a metabolite-sensing genetic switch that binds FMN with high affinity and specificity to regulate the expression of genes involved in the biosynthesis and transport of riboflavin (Serganov et al., 2009). Upon binding FMN, the riboswitch undergoes a conformational change that typically leads to the formation of a rho-independent transcription terminator or the sequestration of the ribosome-binding site, effectively shutting down gene expression (Howe et al., 2015). Because riboswitches are prevalent in bacteria but absent in humans, they represent promising targets for the development of novel classes of antibiotics (Blount & Breaker, 2006). Small molecules like the natural antibiotic Roseoflavin and the synthetic compound Ribocil have been shown to target the FMN riboswitch, inhibiting bacterial growth by mimicking the natural ligand and suppressing essential metabolic pathways (Howe et al., 2015; Ott et al., 2009). This mechanism of action provides a pathway for treating infections caused by pathogens that rely on endogenous riboflavin production.

Other names

RFN elementRiboflavin riboswitchFMN-sensing riboswitch

The drug binds to the aptamer domain of the riboswitch, inducing a conformational change in the expression platform that results in premature transcription termination or inhibition of translation initiation, thereby downregulating genes required for riboflavin biosynthesis (Howe et al., 2015).