Redox-dependent structural changes in the nitrogenase P-cluster.

J W Peters; M H Stowell; S M Soltis; M G Finnegan; M K Johnson; D C Rees

doi:10.1021/bi9626665

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PubMed · 9063865

Redox-dependent structural changes in the nitrogenase P-cluster.

J W Peters·M H Stowell·S M Soltis·M G Finnegan·M K Johnson·D C Rees

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Abstract

The structure of the nitrogenase MoFe-protein from Azotobacter vinelandii has been refined to 2.0 A 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-beta188 O gamma, and the backbone amide of Cys-alpha88. In the native P(N) state, Ser-beta188 O gamma and the amide N of Cys-alpha88 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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Aspergillus Crystallography, X-Ray Electron Spin Resonance Spectroscopy Electron Transport Models, Molecular Molecular Sequence Data Molybdoferredoxin Nitrogenase Oxidation-Reduction Protein Conformation Journal Article Research Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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J W Peters, M H Stowell, S M Soltis, M G Finnegan, M K Johnson, D C Rees. 1997-02-11. Redox-dependent structural changes in the nitrogenase P-cluster.. https://doi.org/10.1021/bi9626665

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