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. Author manuscript; available in PMC: 2021 Jun 24.
Published in final edited form as: Chem Rev. 2020 Mar 4;120(12):5107–5157. doi: 10.1021/acs.chemrev.9b00704

Figure 8.

Figure 8.

The P- and M-clusters of NifDK. The P-clusters can undergo a conversion from the all-ferrous PN state (A) via 2-electron oxidation to the POX state (B). This opens the cluster and causes the cleavage of two Fe–S bonds from the central μ6-sulfide and Fe centers bind to the backbone of α-Cys88 and β-Ser188. The M-cluster is bound in NifD to α-Cys275 and α-His442. The atoms represented as ball-and-stick models, and are colored as follows: Fe, orange; S, yellow; C, grey; O, red; N, blue (PDB IDs: 1MIN and 3MIN).