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Characterization of oxidation states of the Fe-protein from Azotobacter vinlandii

Thesis/Dissertation ·
OSTI ID:5193443
Some of the properties of the (4Fe-4S) cluster of the Fe protein from Azotobacter vinlandii nitrogenase (Av2) were studied by two methods; Fe chelation reactions and Fe exchange reactions. In the presence of the chelator, 2,2-dipyridyl, and MgATP, the oxidized (4Fe-4S) cluster decomposes in a biphasic manner. In the initial fast phase, two Fe are removed; the remainder of the iron is chelated in a much slower process. An intermediate of the chelation reaction, 2Fe-Av2, contains 2Fe/protein. Iron and inorganic sulfur determinations, and visible, EPR, and Moessbauer spectal properties indicate that the 2Fe-Av2 intermediate of the chelation reaction contains a 2Fe-2S cluster. The Fe in the oxidized (4Fe-4S) cluster can be exchanged with radiolabeled iron without loss of activity of the protein. In 100 mM NaCl and MgATP, only two of the Fe in the cluster are exchanged. MgADP prevents exchange of Fe into the cluster. The Fe in the reduced (4Fe-4S) cluster is apparently resistant to exchange with radiolabeled iron. No conditions are found in which significant exchange of iron is observed.
Research Organization:
Minnesota Univ., Minneapolis (USA)
OSTI ID:
5193443
Country of Publication:
United States
Language:
English