한빛사 논문
Wonchull Kang1,*, Chi Chung Lee1,*, Andrew J. Jasniewski1, Markus W. Ribbe1,2,†, Yilin Hu1,†
1Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.
2Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA.
†Corresponding author.
* These authors contributed equally to this work.
Abstract
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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