Table 1. Data-collection and refinement statistics.

Values in parentheses are for the highest resolution shell.

	Na+ TtCutA1	TtCutA1	Na+ PhCutA1
Space group	I23	P3221	P212121
Unit-cell parameters ()
a	83.00	71.75	93.09
b	83.00	71.75	124.25
c	83.00	100.40	50.46
= ()	90	90	90
()	90	120	90
V M (3Da1)	1.85	2.16	1.73
Solvent content (%)	32.99	42.61	28.48
Subunits per asymmetric unit	1	3	6
Data collection
Temperature (K)	100	100	100
X-ray source	BL44B2, SPring-8	Rigaku FR-D	Rigaku FR-D
Detector	MAR CCD 165	R-AXIS IV	R-AXIS IV
Wavelength ()	0.9	1.54178	1.54178
Resolution range ()	401.70 (1.76170)	401.90 (1.991.90)	401.80 (1.88180)
Reflections (total/unique)	324012/10452	801788/23582	324593/53038
R merge † (%)	7.3 (47.9)	8.2 (44.6)	6.0 (32.4)
I/(I)	51.3 (7.9)	17.5 (6.7)	20.7 (4.1)
Completeness (%)	99.8 (100)	95.4 (90.4)	96.3 (86.2)
Refinement statistics
No. of protein atoms	819	2462	5250
No. of water atoms	84	386	688
Bound metal atoms	Na1, Na2		Na1
Reflections (working set/test set)	10452/544	23009/1116	53038/2691
R work ‡/R free §	0.23/0.25	0.19/0.23	0.19/0.23
R.m.s. deviations from ideal values
Bond lengths ()	0.005	0.006	0.005
Bond angles ()	1.3	1.4	1.2
B factors (2)
Wilson plot	19.80	20.10	23.70
Average	27.70	28.65	26.67
Protein atoms	24.6	26.2	26.1
Water atoms	42.0	43.8	42.5
Ramachandran plot (%)
Most favoured	93.5	93.8	93.5
Additionally allowed	6.5	5.8	6.5
Generously allowed	0	0.4	0.0
PDB code	1nza	1v6h	4nyo

^† R _merge = , where I_i(hkl) and I(hkl) are the observed intensity of measurement i and the mean intensity of the reflection with indices hkl, respectively.

^‡ R _work = , where F _obs and F _calc are the observed and calculated structure factors, respectively.

^§ R _free is the R _work calculated for a subset of 5% of the reflections that were omitted from refinement.