The Cyclic di-GMP riboswitch, also known as GEMM RNA motif, is a highly conserved RNA structure that is involved in regulation of a large variety of microbial processes including virulence, motility, and biofilm formation. It serves as a riboswitch that binds directly to cyclic di-guanosine monophosphate [18635805]. Cyclic di-GMP is a second messenger used in signal transduction in a wide variety of bacteria. Cyclic di-GMP is synthesized by proteins with diguanylate cyclase activity. Cyclic di-GMP riboswitch was originally identified by bioinformatics as a conserved RNA-like structure called the "GEMM motif" [17621584]. more

These riboswitches are present in a wide variety of bacteria, and are most common in Firmicutes and Proteobacteria (most commonly in Gamma- and Delta-proteobacteria). The genomes of Geobacter species predicted to have from 4 to 28 instances of this riboswitch. The solved crystal structure of the cyclic di-GMP riboswitch from the tfoX gene from Vibrio cholerae showed that the ligand binds within a three-helix junction that involves base-pairing and extensive base-stacking [19898477].