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- Title
The Nitrogenase FeMo-Cofactor Precursor Formed by NifB Protein: A Diamagnetic Cluster Containing Eight Iron Atoms.
- Authors
Guo, Yisong; Echavarri ‐ Erasun, Carlos; Demuez, Marie; Jiménez ‐ Vicente, Emilio; Bominaar, Emile L.; Rubio, Luis M.
- Abstract
The biological activation of N2 occurs at the FeMo-cofactor, a 7Fe-9S-Mo-C-homocitrate cluster. FeMo-cofactor formation involves assembly of a Fe6-8-SX-C core precursor, NifB-co, which occurs on the NifB protein. Characterization of NifB-co in NifB is complicated by the dynamic nature of the assembly process and the presence of a permanent [4Fe-4S] cluster associated with the radical SAM chemistry for generating the central carbide. We have used the physiological carrier protein, NifX, which has been proposed to bind NifB-co and deliver it to the NifEN protein, upon which FeMo-cofactor assembly is ultimately completed. Preparation of NifX in a fully NifB-co-loaded form provided an opportunity for Mössbauer analysis of NifB-co. The results indicate that NifB-co is a diamagnetic ( S=0) 8-Fe cluster, containing two spectroscopically distinct Fe sites that appear in a 3:1 ratio. DFT analysis of the 57Fe electric hyperfine interactions deduced from the Mössbauer analysis suggests that NifB-co is either a 4Fe2+-4Fe3+ or 6Fe2+-2Fe3+ cluster having valence-delocalized states.
- Subjects
COFACTORS (Biochemistry); IRON-molybdenum alloys; PROTEIN synthesis; CHEMICAL precursors; NITROGENASES; DIAMAGNETISM; IRON; CARBIDES
- Publication
Angewandte Chemie, 2016, Vol 128, Issue 41, p12956
- ISSN
0044-8249
- Publication type
Article
- DOI
10.1002/ange.201606447