Figure 1. Mechanisms for Regulation of Gene Expression by Purine Riboswitches.
(A) Schematic showing control of gene expression by the xpt G-riboswitch through transcriptional termination [23]. Highly conserved residues in the G-box of the aptamer domain are marked in red.
(B) Gene expression regulation by the ydhL A-riboswitch through disruption of the terminator hairpin [24].
(C) Control of gene expression by the add A-riboswitch most likely through translational activation. The Shine-Dalgarno GAA sequence and the initiation codon are both shaded in orange.