6UG0 image
Entry Detail
PDB ID:
6UG0
Keywords:
Title:
N2-bound Nitrogenase MoFe-protein from Azotobacter vinelandii
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2019-09-25
Release Date:
2020-06-24
Method Details:
Experimental Method:
Resolution:
1.83 Å
R-Value Free:
0.25
R-Value Work:
0.21
R-Value Observed:
0.21
Space Group:
P 21 21 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Nitrogenase molybdenum-iron protein alpha chain
Chain IDs:A, C
Chain Length:492
Number of Molecules:2
Biological Source:Azotobacter vinelandii
Polymer Type:polypeptide(L)
Description:Nitrogenase molybdenum-iron protein beta chain
Chain IDs:B, D
Chain Length:523
Number of Molecules:2
Biological Source:Azotobacter vinelandii
Primary Citation
Structural evidence for a dynamic metallocofactor during N2reduction by Mo-nitrogenase.
Science 368 1381 1385 (2020)
PMID: 32554596 DOI: 10.1126/science.aaz6748

Abstact

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 N2 turnover 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.

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Primary Citation of related structures