Table 1. Crystal data and data-collection and structure-refinement statistics.

Values in parentheses are for the outer shell.

	Plate-shaped crystal	Rod-shaped crystal
Crystal data
Space group	C2	P43
Unit-cell parameters (Å)	a = 151.9, b = 48.9, c = 60.2	a = b = 29.3, c = 89.8
Unit-cell volume (Å3)	402141	77213
Asymmetric unit volume (Å3)	100535	19303
Z †	1 [6S RNA]	1 [RNA duplex]
Solvent content (%)	51.1	53.4
Data collection
Beamline	ID29, ESRF	ID23-1, ERSF
Wavelength (Å)	1.0	1.0723
Resolution (Å)	35.7–5.0 (5.2–5.0)	20.7–2.6 (2.7–2.6)
Unique reflections	1264	2330
Completeness (%)	69.7 (74.9)	99.6 (100.0)
R merge ‡ (%)	6.7 (42.5)	9.0 (39.7)
Multiplicity	2.3 (2.2)	7.2 (7.5)
Structure refinement
Resolution range (Å)		20.7–2.6
Used reflections		2330
R factor§ (%)		18.5
R free ¶ (%)		22.8
No. of RNA atoms		517
No. of waters		23
R.m.s.d., bond lengths (Å)		0.006
R.m.s.d., bond angles (°)		1.2

^†Estimated number of 6S RNAs (132 nt) or RNA duplexes (12 bp) in the asymmetric unit.

^‡ R _merge = 100 × .

^§ R factor = 100 × , where |F _obs| and |F _calc| are optimally scaled observed and calculated structure-factor amplitudes, respectively.

^¶Calculated using a random set containing 10% of observations.