Fig. 5: Effect of Mg2+ and F- on EC58 and EC48.
From: An anionic ligand snap-locks a long-range interaction in a magnesium-folded riboswitch
(a, b) Schematics of the fluoride riboswitch in an elongation complex at transcript lengths of 58 and 48 nucleotides, respectively. (c, d) FRET histograms and corresponding TODPs in the absence and presence of Mg2+ and F- for EC58 and EC48, respectively. The FRET histograms are well fitted with two Gaussian peaks for EC58 shown in red and cyan for the mid- and high-FRET states, respectively, with the cumulative fit shown in blue; and a single Gaussian peak for EC48 shown in blue. The percent population of fitted peaks are shown in respective colors in each histogram panel, and the number of molecules that were analyzed is indicated by “N”. A dashed white circle highlights the presence of the SD conformation in TODPs for EC58. (e) Representative time traces for EC48 showing similar EFRET values but different γ values, which were determined using fluorescence intensities of donor (ID) and acceptor (IA) before (pre) and after (post) photobleaching of the acceptor as \({{{{{\rm{\gamma }}}}}}=({{{{{{\rm{I}}}}}}}_{{{{{{\rm{A}}}}}},{{{{{\rm{Pre}}}}}}}-{{{{{{\rm{I}}}}}}}_{{{{{{\rm{A}}}}}},{{{{{\rm{Post}}}}}}})/({{{{{{\rm{I}}}}}}}_{{{{{{\rm{D}}}}}},{{{{{\rm{Post}}}}}}}-{{{{{{\rm{I}}}}}}}_{{{{{{\rm{D}}}}}},{{{{{\rm{Pre}}}}}}})\)38,39. (f) Histogram of the γ-parameter for EC48 in the absence and presence of F- as indicated.
