Mossbauer and EPR Evidence for an All-Ferrous Fe_4S_4 Cluster with S = 4 in the Fe Protein of Nitrogenase

摘要

The data reported here confirm the earlier conclusion of Watt and Reddy that the Fe protein can be reduced to an all-ferrous state. This state can also be produced using the hydroquinone form of the physiological electron donor flavodoxin. Since flavodoxin is known to serve as a one-electron donor under these conditions, this observation suggests a reason for why the Fe protein is a dimer with a single Fe_4S_4 cluster: thus, two molecules of flavodoxin may have to bind for the delivery of two electrons.