EXAFS studies of FeMo-cofactor and MoFe protein. Direct evidence for the long-range Mo-Fe-Fe interaction and cyanide binding to the Mo in FeMo-cofactor

Journal Article · Tue Mar 22 23:00:00 EST 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00085a022· OSTI ID:7019449

Liu, H I ^[1]; Filipponi, A ^[2]; Gavini, N; Burgess, B K ^[3]; Hedman, B ^[4]; Di Cicco, A ^[5]; Natoli, C R ^[6]; Hodgson, K O ^[7]

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1. Stanford Univ., CA (United States)
2. Universita degli Studi dell'Aquila (Italy)
3. Univ. of California, Irvine, CA (United States)
4. Stanford Synchrotron Radiation Lab., CA (United States)
5. Universita degli Studi di Camerino (Italy)
6. INFN, Frascati (Italy)
7. Stanford Univ., CA (United States) Stanford Synchrotron Radiation Lab., CA (United States)

The biological reduction of dinitrogen to ammonia by the nitrogenase system requires the MoFe protein, which contains two iron-molybdenum cofactors (FeMoco) and two Fe-S P-clusters, and the Fe protein, which is the electron donor in catalysis. We report herein a new series of Mo-K edge EXAFS studies of highly concentrated isolated FeMoco, isolated FeMoco plus CN-and the MoFe protein. Very high quality data has been obtained over a wide k-range through improved experimental techniques. In addition, new EXAFS analysis methodology (called GNXAS) based on multiple scattering formalism with further enhancements has been used to analyze the data. Several important results have emerged: for the first time a second shell of Fe atoms at [approximately] 5.1 [angstrom] from the Mo is clearly present in the EXAFS for both FeMoco and the MoFe protein. This provides direct evidence for the [open quotes]intact[close quotes] nature of extracted FeMoco and demonstrates the ability to detect and analyze such long-range absorber-scatter interactions. Second, the EXAFS results give very accurate metrical details of the FeMoco sites, and these differ from those of FeMoco from the X-ray crystal structure of the MoFe protein at its current level of refinement. Finally, using the GNXAS analysis method, it is shown that added CN[sup [minus]] coordinates to Mo in isolated FeMoco. 35 refs., 6 figs.

• OSTI ID: 7019449
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 116:6; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
550200 -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ABSORPTION SPECTROSCOPY
AMMONIA
CATALYSIS
CHALCOGENIDES
CHEMICAL REACTIONS
COMPLEXES
COMPUTERIZED SIMULATION
CRYSTALLOGRAPHY
ELEMENTS
ENZYMES
HYDRIDES
HYDROGEN COMPOUNDS
IRON COMPLEXES
METALLOPROTEINS
MOLYBDENUM COMPLEXES
NITRO-GROUP DEHYDROGENASES
NITROGEN
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGENASE
NONMETALS
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXIDOREDUCTASES
PROTEINS
REDUCTION
SIMULATION
SPECTROSCOPY
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY