Table 1.

Data collection and refinement statistics. See also Table S1 and Figure S1, S2.

Data collection	YrlA Tetraloop	YrlA Tetraloop 3C
Space group	C2221	P63
Cell dimensions
a, b, c (Å)	59.42, 147.12, 101.58	146.46, 146.46, 52.53
α, β, γ(°)	90, 90, 90	90, 90, 120
Resolution (Å)a	50.0-3.0 (3.05-3.0)	50.0-4.3 (4.37-4.30)
Rmerge (%)	8.9 (82.7)	9.6 (>100)
<I>/<σ(I)>	13.5 (2.0)	14.4 (1.0)
Completeness (%)	98.0 (97.0)	99.1 (97.4)
Redundancy	3.6 (3.5)	5.7 (4.8)
CC1/2	1.00(0.93)	1.00(0.67)
Refinement
Resolution (Å)	30.0-3.0
No. reflections	8563 (613)
Rwork/ Rfree (%)	22.3/23.8 (38.1/46.7)
No. atoms
RNA	1722
Ion	12
Water	2
Mean B-factors (Å2)
RNA	140.2
Ion	169.7
Water	125.6
R.m.s. deviations
Bond lengths (Å)	0.009
Bond angles (°)	1.04

^aValues in parentheses are for highest-resolution shell.