The Unusual Metal Clusters of Nitrogenase: Structural Features Revealed by X-Ray Anomalous Diffraction Studies of the MoFe Protein from Clostridium pasteurianum

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 90; no. 3; pp. 1078 - 1082
• Main Authors: BOLIN, J. T, RONCO, A. E, VANCE MORGAN, T, MORTENSON, L. E, NGUYEN-HUU XUONG
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-02-1993; National Acad Sciences; National Academy of Sciences
• Subjects: Analytical, structural and metabolic biochemistry; Atoms; Biochemistry; Biological and medical sciences; Clostridium - enzymology; Clostridium pasteurianum; crystal structure; Crystals; Electron density; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Iron - chemistry; Molecules; Molybdenum - chemistry; Molybdoferredoxin - chemistry; nitrogenase; Oxidoreductases; Patterson function; Protein Conformation; Proteins; Resonance scattering; Scattering, Radiation; Sulfur - chemistry; Symmetry; Wave diffraction; X-Ray Diffraction - methods; Molecular structure; Enzyme; Clostridium pasteurianum; Nitrogenase; Clostridiaceae; Clostridiales; Bacteria; Cofactor; X ray diffraction; Structure function relationship; Iron Sulfur cluster; Ferromolybdoprotein
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.3.1078

Nitrogenase (EC 1.18.6.1) catalyzes the conversion of dinitrogen to ammonia, the central reaction of biological nitrogen fixation. X-ray anomalous diffraction data were analyzed to probe the structures of the metal clusters bound by nitrogenase MoFe protein. In addition to one FeMo cofactor, each half-molecule of MoFe protein binds one large FeS cluster of a type not previously observed in a protein. The FeS cluster contains roughly eight Fe atoms, comprises two subclusters, and is separated from the FeMo cofactor by an edge-to-edge distance of 14 overset⚬mathrm A. The inorganic framework of the FeMo cofactor is not resolved into subclusters, but the Mo atom is located at its periphery. FeMo cofactors in different half-molecules are 70 Å apart and cannot promote binuclear activation of dinitrogen by two Mo atoms.