Mössbauer and EPR Evidence on the Prosthetic Groups of the MoFe Protein

  • B. H. Huynh
  • E. Münck
  • W. H. Orme-Johnson
Conference paper
Part of the NATO Advanced Study Institutes Series book series (ASIC, volume 89)


Spectroscopic evidence strongly suggests the existence of two types of redox centers in the MoFe proteins, designated as the M center and the P cluster. Each MoFe protein was shown to contain two M centers and four P clusters, accounting for 28 of the 30 iron atoms in the molecule. The M center is a spin-coupled complex which contains most probably six irons and one molybdenum atom. It resides in the cofactor and can be stabilized in three oxidation states. The native state MN has a spin S = 3/2 and its ground doublet is EPR active. A one electron oxidation process transforms MN into Mox which is diamagnetic. Under nitrogen fixing conditions, the state MN is reduced into state MR. State MR is not discussed in this manuscript but has been shown to have integer spin S > 0 (1). The P cluster contains four spin-coupled iron atoms, most probably bridged by labile sulfur. Two oxidation states, Pox and PN, have been characterized. The native state PN is diamagnetic. The oxidized state Pox has a half integer spin S ≥ 3/2, and is characterized by a negative zero field parameter D. The nature of the remaining two irons is still nebulous and further investigations are warranted.


Iron Atom Isomer Shift Electric Field Gradient Prosthetic Group Quadrupole Doublet 
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Copyright information

© D. Reidel Publishing Company 1982

Authors and Affiliations

  • B. H. Huynh
    • 1
  • E. Münck
    • 2
  • W. H. Orme-Johnson
    • 3
  1. 1.Department of PhysicsEmory UniversityAtlantaUSA
  2. 2.Gray Freshwater Biological InstituteUniversity of MinnesotaNavarreUSA
  3. 3.Department of ChemistryMassachusetts Institute of TechnologyCambridgeUSA

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