Table 2. Cryo-EM data collection and model statistics.

Dataset	SP1 untreated	SP2 EDTA treated	SP3sym EDTA treated	SP3bent EDTA treated	SP4sym EDTA/TPEN treated	SP4bent EDTA/TPEN treated
Deposition	N/A			N/A	N/A	N/A
PDB		7KZX	7KZZ
EMDB		EMD-23092	EMD-23093
Data collection and processing
Magnification	81,000	81,000	81,000	81,000	81,000	81,000
Voltage (kV)	300	300	300	300	300	300
Electron exposure (e–/Å2)	83	77	65	65	50	50
Defocus range (μm)	1.0-3.0	1.5-3.0	1-2.5	1-2.5	1-2.5	1-2.5
Pixel size (Å)	1.035	1.035	1.048	1.048	1.079	1.079
Symmetry imposed	C2	C1	C2	C1	C2	C1
Initial particle images (no.)	473,960	848,576	1,448,191	1,448,191	1,685,559	1,685,559
Final particle images (no.)	102,390	140,565	151,898	85,207	287,608	140,971
Map resolution (Å)	3.83	4.00	3.42	4.18	3.52	4.66
FSC threshold	0.143	0.143	0.143	0.143	0.143	0.143
Model refinement				MDFFa	MDFFa	MDFFa
Model composition
Nonhydrogen atoms	10416	10446	10470	10446	10468	10446
Protein residues	1362	1361	1364	1361	1364	1361
Ligands	8	0	8	0	0	0
RMS deviations
Bond lengths (Å)	0.004	0.011	0.014	0.012	0.012	0.009
Bond angles (°)	0.884	1.103	2.397	1.275	1.238	1.119
Validation
MolProbity score	2.39	2.31	2.13	2.73	2.41	2.65
Clashscore	20.96	19.88	2.30	40.62	21.56	34.86
Rotamer outliers (%)	0.00	0.00	4.11	0.00	0.00	0.00
CaBLAM outliers (%)	3.88	4.72	5.70	6.02	5.02	4.42
Ramachandran plot
Favored (%)	89.16	91.10	85.00	86.16	88.66	86.84
Allowed (%)	10.84	8.60	11.57	13.61	11.04	13.16
Disallowed (%)	0.00	0.30	3.43	0.22	0.30	0.00
Model vs. data CC (mask)	0.78	0.81	0.78	0.78	0.81	0.82

FSC, forward scatter.

^aModels created by Namdinator, which removes Zn ligands during its fitting process.