Fig. 3. Electron-transfer relay of MtFsr.

MtFsr, shown as cartoon, has the same color code and numbering of its [4Fe‒4S] clusters (balls and sticks) as in the domain representation in Fig. 1. Edge-to-edge distances connecting the clusters are shown as dashes. The distances to the adjacent [4Fe‒4S] clusters of the opposite dimer are shown in red. The primes correspond to the second monomer forming the dimer. The residues binding the clusters are shown as balls and sticks. Carbon atoms are colored by their domain affiliation. Nitrogen, oxygen, sulfur and iron atoms are colored in blue, red, yellow and orange, respectively. Siroheme and FAD are shown as sticks with purple and yellow carbon atoms, respectively.