Table 1.

Experimental restraints and structure statistics for the refined PEMV-1 RNA pseudoknot structure^a

Number of structures	28
NOE distance restraints (22/residue)	704
Intranucleotide	464
Internucleotide	240
Dihedral angle restraints	151
Residual dipolar couplings (1DCH)	118
Sugar	78
Base	40
RMS from experimental restraints
Distance restraints (Å)b, c	0.029 ± 0.002
Dihedral restraints (°)b, c	n/a
Dipolar couplings (Hz)	2.50 ± 0.03
Deviations from idealized geometry
Bonds (Å)	0.007 ± 0.001
Angle (°)	1.57 ± 0.02
Impropers (°)	0.93 ± 0.02
Heavy-atom RMSD (Å)
Overall (residues 4–30, excluding 14 and 20)	1.18 ± 0.14
S1	1.10 ± 0.18
S2	0.86 ± 0.16

^aRefinement of the previous lower resolution structure [PDB codes 1KPZ (average solution structure) and 1KPY (bundle)] through analysis of a 3D ¹³C-separated NOESY spectrum acquired at 900 Hz ¹H frequency (τ_m = 100 ms) and 2D ¹H–¹H NOESY spectra (600 MHz; τ_m = 60 and 280 ms) with the resulting bundle of 28 lowest energy structures refined with 118 sugar and base ¹D_CH residual dipolar coupling restraints obtained from 2D J-modulated CT-HSQC (Ottiger et al., 1998) and CT-TROSY (Boisbouvier et al., 2000) spectra using a three-step simulated annealing protocol essentially identical to that previously described (Cornish et al., 2005, McCallum and Pardi, 2003). A global overlay of a bundle of 28 lowest energy structures and an average structure have been deposited in the RCSB under PDB accession codes 2RP0 and 2RP1, respectively.

^bNo violations >0.5 Å.

^cNo violations >5°.