1H, 13C and 15N assignment of stem-loop SL1 from the 5'-UTR of SARS-CoV-2

Figures

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  Fig. 1. a Secondary structure of 5_SL1 and its genomic position within the 5'-UTR of the SARS-CoV-2 genome. b Detection of the W–C base-pairs U13-A26 and U17-A22 in the lrHNN-COSY experiment (Table 1, XIII.). Adenosine C2H2 resonances (lower spectrum, 1H,13C-HSQC) were used to assign the 2J-N1H2 diagonal peaks and the corresponding uridine N3 cross peaks. Note that the A12 N1H2 resonance is broadened beyond detection. The U13-A22 and U17-A22 correlations are shown in black, the other base-pairs in grey in panel a

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  Fig. 2. Plot of γFIT against PFIT as calculated from ribose 13C chemical shifts according to (Cherepanov et al. 2010). Residues from the apical loop are marked in red, bulge residues in black. C34 is omitted due to its low-field C2′ chemical shift typical for the 3'-terminal nucleotide, resulting in exceptionally high values of the canonical coordinates

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  Fig. 3. Expanded region of the 2D 1H,1H TOCSY experiment (Table 1, XIV.) correlating pyrimidine H5–H6 proton chemical shifts via their 3J coupling. Linewidths are approximately inversely proportional to the base order parameter, resulting in sharp signals for flexible residues that exhibit a lower than the global τc. 1D traces for selected residues are shown in the 2D. The flexible loop residues U18, C19, and C20 and the non-native 3'-terminal c34 are highlighted in red; helical residues U9 and U11 are shown in black