Overall structure of the Burkholderia Guanidine-I riboswitch. (A) Secondary structure. Thin lines with arrowheads denote connectivity. Base pairs are represented with Leontis–Westhof symbols (Leontis and Westhof 2001). Single hydrogen bonds are represented as dashed lines. Red triangle denotes bound guanidine. Asterisks denote residues that participate in A-minor interaction. Wild-type and crystallization construct sequences of the terminal loop of P2 are boxed and blue, respectively. Disordered residues are shown in gray. (B) Cartoon representation of the three-dimensional structure with van der Waals surface of the RNA. Green, yellow, and red spheres denote Mg2+, K+, and guanidine, respectively. (C) Van der Waals surface of the Burkholderia Guanidine-I riboswitch (gray) superimposed with D. dadantii Guanidine-I riboswitch (cartoon; orange). Dashed and solid lines depict the P2 helical axes of D. dadantii and Burkholderia, respectively.
