Fig. 3.

Cofactor insertion into apo-NifDK^RS. (A) Changes in EPR signals after incubation of apo-NifDK^RS with purified FeMo-co in DTH-reducing conditions. Microwave power 1 mW; temperature 5 K. Spectra were obtained from 10 scans. (B) Titration of apo-NifDK^Av (red bars, performed at 30 °C) and apo-NifDK^RS (blue bars, performed at 48 °C) reconstitution with pure NafY–FeMo-co complex (ratios indicated in the x-axis). Control reactions consisted of assays with pure NifDK^Av and NifH^Av at 1:40 molar ratio (C⁺ red bar), or NifB^RS-dependent FeMo-co synthesis and insertion into apo-NifDK^RS (composition of complete reactions in Fig. 5A) (C⁺ blue bar).