Iron EXAFS of Azotobacter vinelandii nitrogenase Mo-Fe and V-Fe proteins

Journal Article · Wed Jun 30 00:00:00 EDT 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00066a019· OSTI ID:5815098

Chen, J ^[1]; Christiansen, J; George, S J ^[2]; Tittsworth, R C; Hales, B J ^[3]; Concouvanis, D ^[4]; Cramer, S P ^[5]

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1. Lawrence Berkeley Lab., CA (United States)
2. Univ. of California, Davis (United States)
3. Louisiana State Univ., Baton Rouge (United States)
4. Univ. of Michigan, Ann Arbor (United States)
5. Lawrence Berkeley Lab., CA (United States) Univ. of California, Davis (United States)

The structure of the iron sites of nitrogenase in dithionite-reduced and thionine-oxidized forms of the Mo-Fe and V-Fe proteins has been investigated using Fe K-edge X-ray absorption spectroscopy. For the dithionite-reduced Azotobacter vinelandii Mo-Fe protein, the dominant EXAFS Fourier transform peaks are assigned to Fe-S and Fe-Fe interactions at approximately 2.32 and 2.64 [angstrom], as expected for Fe-S clusters. An additional Fe-Mo component at 2.73 [angstrom] is required to completely fit the EXAFS in the 1-3-[angstrom] region. In the 3-5-[angstrom] region, a 3.8-[angstrom] Fe-Fe component is identified, with an amplitude corresponding to almost one long Fe-Fe interaction, averaged over all of the iron in the sample. Features that can be explained as Fe-S and Fe-Fe interactions at 4.3 and 4.7 [angstrom] are also observed. A similar pattern of Fe interactions is observed for the reduced A. vinelandii V-Fe protein, except that the short Fe-Mo interaction is no longer required. In both Mo-Fe and V-Fe proteins, the first coordination sphere Fe-S distances contract slightly upon thionine oxidation. The long-range Fe-S and Fe-Fe interactions are very close (within 0.1 [angstrom]) to corresponding distances in Fe[sub 6]S[sub 6] prismane clusters. If the amplitudes are adjusted by assuming that only 14 of 30 nitrogenase irons participate in the M center, then they are consistent with recently proposed crystallographic models. 43 refs., 7 figs., 2 tabs.

• OSTI ID: 5815098
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 115:13; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
NITROGENASE
MOLECULAR STRUCTURE
X-RAY SPECTROSCOPY
PROTEINS
AZOTOBACTER
CRYSTALLOGRAPHY
EXPERIMENTAL DATA
IRON COMPOUNDS
MOLYBDENUM COMPOUNDS
VANADIUM COMPOUNDS
BACTERIA
DATA
ENZYMES
INFORMATION
MICROORGANISMS
NITRO-GROUP DEHYDROGENASES
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDOREDUCTASES
REFRACTORY METAL COMPOUNDS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
550200* - Biochemistry
400201 - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures