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- Title
Catalysis-dependent selenium incorporation and migration in the nitrogenase active site iron-molybdenum cofactor.
- Authors
Spatzal, Thomas; Perez, Kathryn A.; Howard, James B.; Rees, Douglas C.
- Abstract
Dinitrogen reduction in the biological nitrogen cycle is catalyzed by nitrogenase, a two-component metalloenzyme. Understanding of the transformation of the inert resting state of the active site FeMo-cofactor into an activated state capable of reducing dinitrogen remains elusive. Here we report the catalysis dependent, site-selective incorporation of selenium into the FeMo-cofactor from selenocyanate as a newly identified substrate and inhibitor. The 1.60 Å resolution structure reveals selenium occupying the S2B site of FeMo-cofactor in the Azotobacter vinelandii MoFe-protein, a position that was recently identified as the CO-binding site. The Se2B- labeled enzyme retains substrate reduction activity and marks the starting point for a crystallographic pulse-chase experiment of the active site during turnover. Through a series of crystal structures obtained at resolutions of 1.32–1.66 Å , including the CO-inhibited form of Av1- Se2B, the exchangeability of all three belt-sulfur sites is demonstrated, providing direct insights into unforeseen rearrangements of the metal center during catalysis.
- Subjects
NITROGENASES; IRON-molybdenum alloys; NITROGEN cycle; CRYSTAL structure; AZOTOBACTER vinelandii
- Publication
eLife, 2015, p1
- ISSN
2050-084X
- Publication type
Article
- DOI
10.7554/eLife.11620