Table 1. Cryo-EM data collection, reconstruction, model refinement and validation statistics.

Data Collection and processing
Microscope	Titan krios (UCSF)
Camera	K3 detector equipped with GIF
Magnification	60,010
Voltage (kV)	300 kV
Electron exposure (e-/Å2)	51
Defocus range (µm)	−0.5 to −2.0
Pixel size (Å)	0.8332
Software	SerialEM
Reconstruction	CIII2	SCIII2+IV			CIII2 focused	CIV-focused		SC Composite
Software	cryoSPARC	cryoSPARC			Relion	Relion		Phenix
Number of particles	48,111	28,020			38,410	29,348		---
Box size (pixels)	512	512			512	512		512
Final resolution (Å)	3.2	3.8			3.7	3.8		---
Map sharpening B factor (Å2)	67	61			83	77		---
EMDB ID	22445	22449			22450	22447		22448
Model	CIII2		CIV				SC composite
Software	Phenix
Initial model (PDB code)	6Q9E, 6HU9			6HU9, 5B1A			6Q9E, 6HU9, 5B1A
Map/model correlation
Model resolution (Å)	3.3			3.9			3.9
d99 (Å)	3.5			3.9			3.9
FSC model 0.5 (Å)	3.3			3.8			3.8
Map CC (around atoms)	0.88			0.85			0.84
Model composition
Non-hydrogen atoms	32,931			12,772			45,164
Protein residues	3983			1497			5472
Number of chains	20			10			30
Number of ligands and cofactors	8			6			14
Number of lipids	29			20			43
Atomic Displacement Parameters (ADP)
Protein average (Å2)	114.37			38.28			53.17
Ligand average (Å2)	79.11			50.71			66.25
R.m.s. deviations
Bond lengths (Å)	0.005			0.006			0.007
Bond angles (°)	0.704			0.853			1.107
Ramachandran Plot
Favored (%)	93.13			90.75			92.55
Allowed (%)	6.82			9.18			7.40
Disallowed (%)	0.05			0.07			0.06
Validation
MolProbity score	1.97			2.19			2.04
Clash score	10.03			14.21			11.51
Rotamer outliers (%)	0.03			0.08			0.04
EMRinger score	2.80			2.32			2.01
PDB ID	7JRG			7JRO			7JRP