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. Author manuscript; available in PMC: 2019 Feb 16.
Published in final edited form as: J Mol Biol. 2017 Oct 24;430(4):524–536. doi: 10.1016/j.jmb.2017.10.021

Figure 1.

Figure 1

Schematic of U2 stem II model RNAs used in smFRET experiments. (a) Chemical structures of uridine, pseudouridine, ribothymidine. (b) U2 stem II fluctuates between IIa (left) and IIc (right) basepairing. The locations of fluorophore attachment (stars) and pseudouridine incorporation (Ψ) are shown. The green and red stars indicated the donor (Cy3) and acceptor (Cy5) FRET fluorophores, respectively. Basepairing schemes depict stem II conformations observed in the spliceosome by cryo-electron microscopy (cryo-EM) before activation (stem IIa) and after the first catalytic step (stem IIc) [39, 42].