Catalysis-dependent selenium incorporation and migration in the nitrogenase active site iron-molybdenum cofactor
- California Institute of Technology (CalTech), Pasadena, CA (United States). Howard Hughes Medical Inst.; California Institute of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering
- California Institute of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering
- California Institute of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering; Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Biochemistry, Molecular Biology and Biophysics
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.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science Division
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1628840
- Journal Information:
- eLife, Vol. 4; ISSN 2050-084X
- Publisher:
- eLife Sciences Publications, Ltd.Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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