Nitrogen molybdenum iron protein

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... 

Figure 24.2. Nitrogen Fixation. Electrons flow from ferredoxin to the reductase (iron protein, or Fe protein) to nitrogenase (molybdenum-iron protein, or MoFe protein) to reduce nitrogen to ammonia. ATP hydrolysis within the reductase drives conformational changes necessary for the efficient transfer of electrons.

The enzyme system for nitrogen fixation consists of two separate proteins. Nitrogenase (also called component I or molybdenum-iron protein) catalyzes the reduction of N2. The other, nitrogenase reductase (also called component II or iron protein), transfers electrons from ferredoxin or flavodoxin to nitrogenase (Figure 20.4)... 

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. 

Biological nitrogen fixation is accomplished through the catalytic action of an enzyme known as nitrogenase. Nitrogenase consists of two distinct proteins which contain molybdenum, iron, and sulfur. Because the nitrogenase proteins are denatured by exposure to... 

A nitrogenase is a redox enzyme with multi-functions which comprised of MoFe-protein and Fe-protein. The molecular weight of MoFe-protein is about 2,20,000 and it contains two molybdenum atoms, 24-33 iron atoms and 24 27 sulfur atoms. The molecular weight of iron-protein is about 60,000 and it contains four irons and four sulfur atoms. They are very complicated. One possible mechanism of nitrogen fixation is that the MoFe-protein may bind in coordination with one end of dinitrogen molecule. The electron from Fe-S part in the cluster of Fe-protein and the proton from the solution may supply to dinitrogen molecule. 

---