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). 

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... 

Each P-cluster is actually a joined pair of cubane-type clusters, one Fe4S4 and one Fe4S3 with two bridging cysteine -SH groups and one iron atom bonded to three sulfide sulfur atoms (Fig. 24-3).17/23 The FeMo-coenzyme can be released from the MoFe-protein by acid denaturation followed by extraction with dimethylformamide.24 While homocitrate was identified as a component of the isolated coenzyme, the three-dimensional structure of FeMo-co was deduced from X-ray crystallography of the intact molybdenum-iron protein.14/17/18... 

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. 

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. 

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. 

The other component, the molybdenum -iron protein (dinitrogenase, molybdoferredoxin, or component I), contains both iron and molybdenum as well as labile sulfide. It is a mixed (tt2P2) tetramer of 240-kDa mass and an analytical metal ion composition Mo2Fe3oS25. However, the X-ray structure " suggests the composition Mo2Fe34S35 The MoFe protein is a ... 

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. 

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