Resonance Raman studies of the [4Fe-4S] to [2Fe-2S] cluster conversion in the iron protein of nitrogenase.
Resonance Raman spectroscopy has been used to investigate the Fe-S stretching modes of the [4Fe-4S]2+ cluster in the oxidized iron protein of Clostridium pasteurianum nitrogenase. The results are consistent with a cubane [4Fe-4S] cluster having effective Td symmetry with cysteinyl coordination for each iron. In accord with previous optical and EPR studies [(1984) Biochemistry 23, 2118-2122], treatment with the iron chelator alpha, alpha'-dipyridyl in the presence of MgATP is shown to effect cluster conversion to a [2Fe-2S]2+ cluster. Resonance Raman data also indicate that partial conversion to a [2Fe-2S]2+ cluster is induced by thionine-oxidation in the presence of MgATP in the absence of an iron chelator. This result suggests new explanations for the dramatic change in the CD spectrum that accompanies MgATP-binding to the oxidized Fe protein and the anomalous resonance Raman spectra of thionine-oxidized Clostridium pasteurianum bidirectional hydrogenase.
Fu
W G
WG
Center for Metalloenzyme Studies, University of Georgia, Athens 30602.
Morgan
T V
TV
Mortenson
L E
LE
Johnson
M K
MK
D015082:2,2'-Dipyridyl / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D002942:Circular Dichroism; D003013:Clostridium / Q000201:enzymology; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009591:Nitrogenase / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
D007506:Iron-Sulfur Proteins; D015082:2,2'-Dipyridyl; D000255:Adenosine Triphosphate; D009591:Nitrogenase