Studies on the heme and H2-uptake reaction from Azotobacter vinelandii bacterial ferritin

Bacterial ferritin of Azotobacter vinelandii (AvBF) is directly able to pick electrons up for iron release from or transfer them for storage to a platinum electrode in the absence of mediator or other reducer. The ferritin containing the structure of heme-Co²⁺ in part shows weakened activity to electrode and decreases the rate of iron release greatly. A reversible reduction process of the ferritin is observed by the spectral change regularly ranging from 310 to 260 nm under mixed gases containing 98% H₂ and 2% to O₂. The activity of nitrogen fixation from the whole cell of A. vinelandii increases greatly by H₂ reduction with potentials ranging from −397 to −425 mV vs. NHE, indicating two important roles of H₂-uptake reaction of the ferritin in increasing activity of nitrogen fixation and in supplying iron to synthesize nitrogenase.