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

Abstract

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.