Structural and Mechanistic Insights into CO 2 Activation by Nitrogenase Iron Protein

• Published in: Chemistry : a European journal 2019-10, Vol.25 (57), p.13078-13082
• Main Authors: Rettberg, Lee A, Stiebritz, Martin T, Kang, Wonchull, Lee, Chi Chung, Ribbe, Markus W, Hu, Yilin
• Format: Article
• Language: English
• Subjects: Azotobacter vinelandii - chemistry; Carbon Dioxide - chemistry; Carbon Dioxide - metabolism; Catalysis; Iron-Sulfur Proteins - chemistry; Nitrogenase - chemistry; Oxidation-Reduction; Oxidoreductases - chemistry; Oxidoreductases - metabolism; Protons
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201903387

The Fe protein of nitrogenase catalyzes the ambient reduction of CO when its cluster is present in the all-ferrous, [Fe S ] oxidation state. Here, we report a combined structural and theoretical study that probes the unique reactivity of the all-ferrous Fe protein toward CO . Structural comparisons of the Azotobacter vinelandii Fe protein in the [Fe S ] and [Fe S ] states point to a possible asymmetric functionality of a highly conserved Arg pair in CO binding and reduction. Density functional theory (DFT) calculations provide further support for the asymmetric coordination of O by the "proximal" Arg and binding of C to a unique Fe atom of the all-ferrous cluster, followed by donation of protons by the proximate guanidinium group of Arg that eventually results in the scission of a C-O bond. These results provide important mechanistic and structural insights into CO activation by a surface-exposed, scaffold-held [Fe S ] cluster.