Fig. 2. NifD2K2 species characterized in this work. (A) SDS-PAGE analysis of proteins isolated by one-step Strep-tag affinity purification (1), and ΔHΔZNifD2K2 (2) and ΔHΔZNifD2K2W2 (3) isolated by ion-exchange chromatography of the sample shown in (1). Molecular weight standards are shown on the left lane. The presence of a small amount of a ΔHΔZNifD2K2NafHX species (less than 8% of the total sample) in (3) was revealed by SDS-PAGE analysis of more concentrated samples as shown in Fig. S1.† (B) Schematic representation of samples shown in (A). Interaction of NifW at the interface of NifD2K2 is only shown for convenience and has not been experimentally established. Corresponding X-band EPR spectra are provided in Fig. S2.†.
