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% H-2 and 2% to O-2. The activity of nitrogen fixation from the whole cell of A. vinelandii increases greatly by H-2 reduction with potentials ranging from -397 to -425 mV vs. NHE, indicating two important roles of H-2-uptake reaction of the ferritin in increasing activity of nitrogen fixation and in supplying iron to synthesize nitrogenase. (C) 1999 Elsevier Science S.A. All rights reserved.