A Conformational Mimic of the MgATP-Bound "On State" of the Nitrogenase Iron Protein.Sen, S., Igarashi, R., Smith, A., Johnson, M.K., Seefeldt, L.C., Peters, J.W.
(2004) Biochemistry 43: 1787-1797
- PubMed: 14967020
- DOI: https://doi.org/10.1021/bi0358465
- Primary Citation of Related Structures:
- PubMed Abstract:
The crystal structure of a nitrogenase Fe protein single site deletion variant reveals a distinctly new conformation of the Fe protein and indicates that, upon binding of MgATP, the Fe protein undergoes a dramatic conformational change that is largely manifested in the rigid-body reorientation of the homodimeric Fe protein subunits with respect to one another. The observed conformational state allows the rationalization of a model of structurally and chemically complementary interactions that occur upon initial complex formation with the MoFe protein component that are distinct from the protein-protein interactions that have been characterized previously for stabilized nitrogenase complexes. The crystallographic results, in combination with complementary UV-visible absorption, EPR, and resonance Raman spectroscopic data, indicate that the [4Fe-4S] cluster of both the Fe protein deletion variant and the native Fe protein in the presence of MgATP can reversibly cycle between a regular cubane-type [4Fe-4S] cluster in the reduced state and a cleaved form involving two [2Fe-2S] fragments in the oxidized state. Resonance Raman studies indicate that this novel cluster conversion is induced by glycerol, and the crystallographic data suggest that glycerol is bound as a bridging bidentate ligand to both [2Fe-2S] cluster fragments in the oxidized state.
Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA.