The Nitrogenase FeMo-Cofactor Precursor Formed by NifB Protein: A Diamagnetic Cluster Containing Eight Iron Atoms.
Angew Chem Int Ed Engl
; 55(41): 12764-7, 2016 10 04.
Article
em En
| MEDLINE
| ID: mdl-27611968
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 31 ratio. DFT analysis of the (57) Fe electric hyperfine interactions deduced from the Mössbauer analysis suggests that NifB-co is either a 4Fe(2+) -4Fe(3+) or 6Fe(2+) -2Fe(3+) cluster having valence-delocalized states.
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Base de dados:
MEDLINE
Assunto principal:
Compostos de Ferro
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Ferro
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Molibdoferredoxina
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Nitrogenase
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article