NAD+-II riboswitch

The NAD+-II riboswitch is a structured noncoding RNA domain discovered in bacterial mRNAs that serves as a ligand-activated genetic regulatory element. It specifically recognizes and binds nicotinamide adenine dinucleotide (NAD+), nicotinamide mononucleotide (NMN), and nicotinamide riboside (NR). This riboswitch is termed “NAD+-II” (or class II NAD+ riboswitch) to distinguish it from the NAD+-I riboswitch. It features one aptamer domain (unlike the tandem arrangement in NAD+-I)[6]. Structural studies reveal that it contains complex tertiary RNA folds and forms two distinct ligand-binding pockets that can each bind one ligand molecule predominantly via the nicotinamide moiety of NAD+ or its derivatives[1][3][2]. The NAD+-II riboswitch is typically found upstream of pnuC genes, which encode NR transporters crucial for NAD+ biosynthesis in bacteria and is thus implicated in the regulation of NAD+ transporter expression[5]. While this riboswitch is functionally important for bacterial metabolism and gene regulation, it is not classified as a therapeutic target (receptor, enzyme, transporter, etc.), nor is it currently associated with human disease, pharmacological intervention, or biomarker utility in clinical settings[5][3]. Its value resides in regulating cofactor metabolism and as a model for RNA structure and ligand recognition[3].

Other names

NAD-II riboswitchclass-II NAD+ riboswitchpnuC motifNAD+-II RNA