Extended Data Table 1.

Crystallographic data collection and refinement statistics

Initial ligand State	Mfn1IMB GMPPCP apo	Mfn1IMB GMPPCP apo	Mfn1IMCT109A GTP GTP-bound	Mfn1IMC GDP•AIF4− Transition-like	Mfn1IMCT109A GTP GDP-bound	Mfn1IMA GTPyS GTPyS-bound	Mfn1IMA GDP GDP-bound
Data collection
Data Set	Native	SeMet	Native	Native	Native	Native	Native
Space group	P212121	P212121	P212121	C2	P212121	C2221	P3121
Cell dimensions
a, b, c(Å)	51.8, 110.9, 112.4	51.6, 110.2, 111.3	70.6, 72.4, 95.3	104.1,46.0, 146.2	70.4, 72.9, 95.0	127.6, 143.1, 159.0	93.6,93.6, 114.1
α, β, γ(°)	90	90	90	92.2	90	90	120
Wavelength (Å)	0.91800	0.97915	0.97915	0.91800	0.97915	0.91800	0.91800
Resolution (Å)	47.0-2.2 (6.55-2.2)	49.7-2.3 (6.84-2.3)	44.7-1.6(4.79-1.6)	48.7-2.8(8.30-2.8)	44.7-1.8(5.37-1.8)	47.7-6.1 (16.77-6.1)	46.8-4.3(12.49-4.3)
Rsym*	0.068 (0.438)	0.060 (0.494)	0.043 (0.583)	0.066 (0.629)	0.048 (0.517)	0.0470 (0.522)	0.064 (0.537)
I/σ(I)	18.08(4.27)	21.22 (4.14)	25.54 (3.33)	20.55 (3.02)	25.08(4.12)	19.28(3.32)	17.81 (4.62)
Completeness (%)	99.4 (98.1)	99.5 (97.7)	89.4 (99.7)	99.1 (97.0)	98.9 (98.8)	98.3 (99.8)	97.2 (95.0)
Redundancy	7.9 (8.0)	7.7 (7.5)	7.1 (7.2)	7.4 (7.4)	7.9(8.1)	5.4 (5.4)	10.4(10.8)
Refinement
Resolution (Å)	39.5-2.2		29.1-1.6	48.7-2.8	29.0-1.8
No. reflections	33374		57847	24264	45448
Rwork/Rfree	0.175/0.214		0.179/0.215	0.201/0.258	0.177/0.204
No. atoms
Protein	3291		3224	6484	3137
Ligand/ion	0		34	64	28
Water	184		427	4	273
B-factors
Protein	57.5		33.6	106.9	43.4
Ligand/ion	0		30.8	84.0	36.3
Water	55.3		43.2	68.9	48.3
R.m.s. deviations
Bond lengths (Å)	0.007		0.005	0.012	0.006
Bond angles (°)	0.753		0.812	1.471	0.763

^*Numbers in parentheses represent values from the highest resolution shell.