Daas P J, Hagen W R, Keltjens J T, Vogels G D
Department of Microbiology, Faculty of Science, University of Nijmegen, The Netherlands.
FEBS Lett. 1994 Dec 19;356(2-3):342-4. doi: 10.1016/0014-5793(94)01313-6.
Ferredoxin was purified from methanol-grown Methanosarcina barkeri strain MS. It was isolated as a dimer with a subunit molecular weight of 6,200. The protein contained 7.4 mol iron and 7.2 mol acid-labile sulfur per monomer. In the reduced state the ferredoxin exhibited an EPR spectrum characteristic of two spin-coupled [4Fe-4S]1+ clusters. The EM of the [4Fe-4S]2+:1+ couple was -322 mV +/- 3 mV vs. NHE at 21 degrees C and pH 7.0. The midpoint potential was temperature but not pH dependent. At the physiological temperature of 37 degrees C the Em was -340 mV.
