FIGURE 4.
Structure models of SreA aptamer and riboswitch including structure cassettes. (A) SHAPE-informed secondary structure of the SreA aptamer with flanking structure cassettes, including expected four-way junction structure and P1–4 helices characteristic of SAM-I riboswitches. (B) SHAPE data-independent model of the SreA riboswitch with included structure cassettes and (C) equivalent energy model including pairing with 3′ structure cassette. (D) The SHAPE-informed secondary structure model of the cassette-containing SreA riboswitch includes unintended base pairs with a structure cassette and yielded a model incongruent with SAM-1 riboswitches.
