Studies on the heme and H-2-uptake reaction from Azotobacter vinelandii bacterial ferritin

Bacterial ferritin of Azotobacter vinelandii (AvBF) is directly able to pic k electrons up for iron release from or transfer them for storage to a plat inum electrode in the absence of mediator or other reducer. The ferritin co ntaining the structure of heme-Co2+ in part shows weakened activity to elec trode and decreases the rate of iron release greatly. A reversible reductio n process of the ferritin is observed by the spectral change regularly rang ing 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 incr eases 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 ferr itin in increasing activity of nitrogen fixation and in supplying iron to s ynthesize nitrogenase. (C) 1999 Elsevier Science S.A. All rights reserved.