Fig. 3.

Regulation of transcription by a c-AMP-GMP riboswitch. (A) The genes downstream of the pilM riboswitch in G. metallireducens. Genes in black boxes are putatively involved in exoelectrogenesis. Gene sizes and gaps are not drawn to scale. (B) Predicted sequence and secondary structure of 127 pilM from G. metallireducens in the presence of c-AMP-GMP. The predicted expression platform consists of an intrinsic terminator stem highlighted in gray followed by a run of U residues. (C) Single-round in vitro transcription assays using a DNA template corresponding to the riboswitch depicted in B in the absence (‒) or presence of various cyclic dinucleotides at the concentrations indicated. (Top) PAGE separation of transcripts where FL and T designate full-length and terminated products, respectively. (Bottom) Plot of the fraction of full-length RNA transcripts produced as determined from the PAGE image.