An Atomic-Level Mechanism for Molybdenum Nitrogenase. Part 1. Reduction of Dinitrogen

• Published in: Biochemistry (Easton) 2002-11, Vol.41 (47), p.13934-13945
• Main Author: Durrant, Marcus C
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Apoproteins - chemistry; Apoproteins - metabolism; Azotobacter vinelandii - metabolism; Bacterial Proteins; Binding Sites; Glutamine; Klebsiella pneumoniae - metabolism; Ligands; Models, Molecular; Molybdoferredoxin - chemistry; Molybdoferredoxin - metabolism; Mutagenesis, Site-Directed; Nitrogen Oxides - pharmacokinetics; Oxidation-Reduction; Protein Conformation; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi025623z

The properties of the Fe and Mo sites of the iron−molybdenum cofactor of nitrogenase with respect to binding and activation of N2 have been studied by molecular mechanics calculations on the local protein environment and by density functional theory (DFT) calculations on subsections of the cofactor. The DFT calculations indicate that the homocitrate ligand of the cofactor can become monodentate on reduction, allowing N2 to bind at Mo. In addition, the neighboring Fe atom plays a crucial role in N2 reduction by stabilizing the initial reduced N2 species and by facilitating cleavage of the N−N bond. The various possible isomers for partially reduced N2 intermediates have been compared by DFT, and a detailed model for the reduction of N2 is developed based on these results, together with chemical precedents and the available biochemical data for nitrogenase.