Table S2.

Comparison of crystallographic statistics of apo-CeuE, Crystal II, and Crystal III

	Structure
Crystallographic parameters	apo-CeuE	{(CeuE)3-[Fe(bisDHBS)]2−2[Fe]} Crystal II	{(CeuE)3[Fe(bisDHBS)]2−[Fe(DHBS)2]3−2} Crystal III
Average B value for whole chain
Chain A, Å2	29.3	39.1	30.4
Chain B, Å2	28.8	49.1	33.5
Chain C, Å2	30.2	41.0	30.5
Cell parameters
Cell parameters, Å	a = 56.95, b = 62.74, c = 67.98	a = 58.46, b = 63.02, c = 67.01	a = 58.07, b = 63.09, c = 67.16
Cell parameters, °	α = 82.19, β = 76.74, γ = 75.96	α = 83.36, β = 76.57, γ = 78.24	α = 83.09, β = 76.90, γ = 79.21
Cell volume, Å3	228,507	234,627	234,495
PDB ID code	3ZKW	5ADW	5ADV