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Redox-Dependent Structural Changes in the Nitrogenase P-Cluster

Peters, John W. and Stowell, Michael H. B. and Soltis, S. Michael and Finnegan, Michael G. and Johnson, Michael K. and Rees, Douglas C. (1997) Redox-Dependent Structural Changes in the Nitrogenase P-Cluster. Biochemistry, 36 (6). pp. 1181-1187. ISSN 0006-2960. doi:10.1021/bi9626665.

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The structure of the nitrogenase MoFe-protein from Azotobacter vinelandii has been refined to 2.0 Å resolution in two oxidation states. EPR studies on the crystals indicate that the structures correspond to the spectroscopically assigned oxidized (P^(OX)/M^(OX)) and the native or dithionite-reduced (P^(N)/M^(N)) forms of the enzyme. Both MoFe-protein structures are essentially identical, with the exception of the P-cluster. The MoFe-protein P-cluster in each state is found to contain eight Fe and seven S atoms. Interconversion between the two redox states involves movement of two Fe atoms and an exchange of protein coordination for ligands supplied by a central S atom. In the oxidized P^(OX) state, the cluster is coordinated by the protein through six cysteine ligands, Ser-β188 Oγ, and the backbone amide of Cys-α88. In the native P^(N) state, Ser-β188 Oγ and the amide N of Cys-α88 no longer coordinate the cluster due to movement of their coordinated Fe atoms toward the central sulfur. Consequently, this central sulfur adopts a distorted octahedral environment with six surrounding Fe atoms. A previously described model of the P-cluster containing 8Fe-8S likely reflects the inappropriate modeling of a single structure to a mixture of these two P-cluster redox states. These observed redox-mediated structural changes of the P-cluster suggest a role for this cluster in coupling electron transfer and proton transfer in nitrogenase.

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Rees, Douglas C.0000-0003-4073-1185
Additional Information:© 1997 American Chemical Society. Received October 24, 1996. Discussions with J. B. Howard are gratefully acknowledged. This work was supported by NSF DMB 91-18689 (D.C.R.), NIH GM51962 (M.K.J.), and an NIH postdoctoral fellowship (GM18142) to J.W.P. The rotation camera facility at the Stanford Synchrotron Radiation Laboratory is supported by the DOE Office of Basic Energy Sciences and the NIH Biomedical Technology Program, Division of Research Resources.
Funding AgencyGrant Number
NSFDMB 91-18689
NIH Postdoctoral FellowshipGM18142
Department of Energy (DOE)UNSPECIFIED
NIH Biomedical Technology ProgramUNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20140805-113458653
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Official Citation:Redox-Dependent Structural Changes in the Nitrogenase P-Cluster John W. Peters, Michael H. B. Stowell, S. Michael Soltis, Michael G. Finnegan, Michael K. Johnson, and Douglas C. Rees Biochemistry 1997 36 (6), 1181-1187
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ID Code:47974
Deposited On:05 Aug 2014 20:45
Last Modified:10 Nov 2021 17:52

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