Figure 4.

The [4Fe-4S] D-cluster in C45G/T50C Dv CODH crystals decays over time in air, whereas the B- and C-clusters remain intact. (A) 2Fo-Fc electron density at the D-cluster for crystals harvested immediately after removal from the anaerobic chamber. (B) 2Fo-Fc electron density for the D-cluster 2 h after the crystal was removed from the anaerobic chamber. (C) 2Fo-Fc electron density for the D-cluster 2 days after the crystal was removed from the anaerobic chamber. (D) 2Fo-Fc electron density for the B-cluster 2 days after the crystal was removed from the anaerobic chamber. (E) 2Fo-Fc electron density for the oxidized C-cluster 2 days after the crystal was removed from the anaerobic chamber. Electron density (blue mesh) is contoured to 1σ. Protein is shown as in Figure 2 with the addition of N in blue and Ni in green for the C-cluster. See Figure S4 for comparison to the stability of the WT [2Fe-2S] D-cluster, B-cluster, and C-cluster after 2 days in air.⁷