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. 2014 Apr 29;42(10):6753–6761. doi: 10.1093/nar/gku262

Figure 1.

Figure 1.

Models for riboswitch function. In the equilibrium model (top), a newly transcribed RNA can adopt a conformation in which the ribosome binding site (RBS) is paired and translation is inefficient. This conformation is in equilibrium with a conformation in which the RBS is free (efficient translation). The presence of theophylline (red star) shifts the equilibrium to favor the RBS-free conformation. In the kinetic trapping model (bottom), in the absence of theophylline, the nascent RNA adopts a conformation in which the RBS is paired and translation is inefficient. If theophylline is present during transcription, the theophylline-bound RNA adopts a conformation in which the RBS is free and translation is efficient. In the kinetic trapping model, the free and bound structures do not equilibrate on the timescale of the experiment.