Figure 2.

Unimolecular constructs of the (A) human and (B) Arabidopsis U12–U6_atac snRNA complexes used for NMR experiments. In each case, a stable UUCG tetraloop (in gray font) was used to connect the 3′ truncated U12 strand and the 5′ end of an abbreviated U6_atac strand. The catalytic triad AGC (GGC in Arabidopsis) and ISL bulge elements implicated in folding to form a catalytic complex (highlighted in pink, along with the final two nucleotides of the GGAGAGA loop not included in this construct) are preserved in the unimolecular constructs; numbering of nucleotides for preserved elements in the corresponding snRNAs is the same as in Figure 1B,C/D. Lines denoting Watson–Crick base pairs and dots denoting G·U pairs are those identified in NMR spectra reported here.