Extended Data Fig. 3: Solution characterization of the 2:2:1 complex and FeSII homodimer.
From: Structural basis for the conformational protection of nitrogenase from O2
a, Sedimentation velocity/analytical ultracentrifugation (AUC) profiles of a 1MoFeP:2FeP:2FeSII mixture containing reduced MoFeP, reduced FeP, and oxidized FeSII at different concentrations of total protein (25 µM, 50 µM, and 100 µM). The data suggest that the formation of the 2:2:1 complex and higher order oligomers is concentration dependent. b, AUC profile of the all-oxidized MoFeP:FeP:FeSII mixture (50 µM total concentration), highlighting that the protective complex/polymer can form without the need of electron transfer between FeP and FeSII. c, AUC profiles of reduced (grey) and oxidized (magenta) FeSII (80 μM). Both display the same sedimentation peak and molecular weight estimates representative of a dimeric species. Compared to the sedimentation profile of the oxidized FeSII, the AUC profile of the reduced FeSII displays a broader peak, suggesting the conformationally dynamic nature of the FeSII homodimer in the reduced state in solution. d, Circular dichroism spectra of reduced (grey) and oxidized (magenta) FeSII at 10 μM concentration, highlighting the differences in secondary structure observed between these samples.
