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Structural evidence for a dynamic metallocofactor during N 2 reduction by Mo-nitrogenase

Journal Article · · Science
 [1];  [2];  [2];  [3];  [2]
  1. Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.; OSTI
  2. Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.
  3. Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.; Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA.

The enzyme nitrogenase uses a suite of complex metallocofactors to reduce dinitrogen (N2) to ammonia. Mechanistic details of this reaction remain sparse. We report a 1.83-angstrom crystal structure of the nitrogenase molybdenum-iron (MoFe) protein captured under physiological N2turnover conditions. This structure reveals asymmetric displacements of the cofactor belt sulfurs (S2B or S3A and S5A) with distinct dinitrogen species in the two αβ dimers of the protein. The sulfur-displaced sites are distinct in the ability of protein ligands to donate protons to the bound dinitrogen species, as well as the elongation of either the Mo–O5 (carboxyl) or Mo–O7 (hydroxyl) distance that switches the Mo-homocitrate ligation from bidentate to monodentate. These results highlight the dynamic nature of the cofactor during catalysis and provide evidence for participation of all belt-sulfur sites in this process.

Research Organization:
Univ. of California, Irvine, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
DOE Contract Number:
SC0016510
OSTI ID:
1803014
Journal Information:
Science, Journal Name: Science Journal Issue: 6497 Vol. 368; ISSN 0036-8075
Publisher:
AAAS
Country of Publication:
United States
Language:
English

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