Nitrogenase molybdenum-iron protein structure

B. Nitrogenase Molybdenum-Iron Protein Structural Description of the Nitrogenase Proteins... 

C. Nitrogenase Molybdenum-Iron Protein Structure Structures of the Metal Centers of Nitrogenase... 

Kim, J. and D.C. Rees. Structural models for the metal centers in the nitrogenase molybdenum-iron protein. Science 257,1677-1682 (1992). 

Kim, J. Rees, D.C. (1992). Crystallographic structure and functional implications of the nitrogenase molybdenum-iron protein from Azotobacter vinelandii. Nature (London) 360,553-560. 

Bolen, J.T., Cambasso, N., Muchmore, S.W., Morgan, T.V., and Mortenson, L. E. (1993) Structure and Environment of metal clusters of the nitrogenase molybdenum iron protein from Clostridium pasterianum, in Stiefel, E.I., Coucouvanis, D., and ewton, W.E. (eds.), Molibdenum Enzymes, Cofactors, and Model Systems, Am. Chem. Soc., Wahington, DC. 

VU Fig. 28.18 The structures of the two types of cluster unit present in the nitrogenase molybdenum-iron protein isolated from Azotobacter vinelandii (a) the P-cluster in its reduced state and (b) the FeMo cofactor. Colour code Fe, green Mo, pale grey S, yellow C, grey N, blue O, red. Each non-terminated stick represents the connection of a coordinated amino acid to the protein backbone. 

T. V. Morgan and L. E. Mortenson, Structure and environment of metal clusters in the nitrogenase molybdenum-iron protein from Clostridium pasteurianum, in Molybdenum Enzymes, Cofactors and Model Systems , eds. E. I. Stiefel,... 

Figure 4.2. Schematic models of Fe-Mo cofactor with possible binding of dinitrogen substrate (a) and P cluster (b). Y indicates a bridging ligand. (Part a adapted, with permission, from Kim, J., and Rees, D. C. Structural models for metal centres in the nitrogenase molybdenum-iron protein. Science 257 1677-82. Copyright 1992, American Association for the Advancement of Science. Part b adapted, with permission, from Chan, M. K., Kim, J., and Rees, D. C. The nitrogenase Fe-Mo-cofactor and P-cluster pair 2.2A resolution structures. Science 260 792-4. Copyright 1993, American Association for the Advancement of Science.)...

Kim, J., and D. Rees. Crystallographic Structure and Functional Implications of the Nitrogenase Molybdenum-iron Protein from Azotohacter vinelandii. Nature 3 0, 553-560 (1992). [X-ray crystallogra-... 

In 1930, Hermann Bortels (1902-1979) recognised that nitrogen fixation is a molybdenum-dependent process. Obviously, the nitrogenases from Rhizobium meliloti, Azotobacter vinelandii and Clostridium pasteurianum have a similar constitution. In 1966, Leonard E. Mortenson identified for the first time an Fe- and a MoFe-protein as parts of the nitrogenase enzyme system. The exact structure of the nitrogenase-molybdenum-iron protein from Azotobacter vinelandii [28] was clarified in 1992, and that from Clostridium pasteurianum [29] in 1993, both by Douglas C. Rees. [30] The Fe-protein is a y2-dimer with a molar mass of some 60,000 Daltons, and the MoFe-protein is an ca. 

MgATP hydrolysis and, 47 189-191 nitrogenase complex, 47 186-189 substrates, 47 192-202 molybdenum iron proteins, 47 161, 166-174, 176-183, 191-192 structure, 47 162-164, 166-170 nitrogen fixation role, 36 78 in nitrogen fixation systems, 27 265-266 noncomplementary reactions with Sn", 10 215... 

The sequential electron transfer path in nitrogenase is followed first models of the Fe4S4 cluster of the iron-protein are discussed, then mimics of the P-cluster in the molybdenum-iron protein, and finally structural and functional models of the FeMo-cofactor are summarized. 

Mo-nitrogenase is the only one for which botli detailed structural and mechanistic data are available [9, 18]. The enzymatic complex comprises two proteins the iron-protein and the molybdenum-iron-protein. 

The proteins involved in the reduction of nitrogen to ammonia and other accessible forms contain several such clusters coupled with molybdenum centres. The structure of the central iron-molybdenum cluster at the centre of nitrogenase is shown in Fig. 10-9. Even with the detailed knowledge of this reaction site, the mode of action of nitrogenase is not understood. 

Avaible experimental structural and kinetics data and energetic considerations indicate two plausible roles of ATP in the nitrogenase reduction a) the triggering of electron transfer from iron protein to iron-molybdenum protein (Howard and Rees, 1994 Rees and Howard, 2000) and the strengthening reducing power of the enzyme catalytic redox centers (Likhtenshtein and Shilov, 1977, Likhenshtein 1988a, Syrtsova and Timofeeva, 2001 see also Section 6.1.4). 

Vanadium nitrogenase is produced by certain bacteria grown in molybdenum-deficient environments. It is effective in the reduction of N2 and other nitrogenase substrates, although with less activity than the Mo—Nase. The enzyme resembles the Mo analogue (see Sections 17-E-10 and 18-C-13) in the construction and structure of the prosthetic groups, as well as in its functions.101 It consists of a FeV protein, FeVco, and an iron protein (a 4Fe—4S ferredoxin). 

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