Iron-proteins

W. A. Bulen, J. R. LeComte, R. C. Bums, and J. Hinkson, in A. San Pietro, ed., Non-Heme Iron Proteins Role in Lnerg Conversion Antioch Press, Yellow Springs, Ohio, 1965, p. 261. 

G Backes, Y Mino, TM Loehr, TE Meyer, MA Cusanovich, WV Sweeny, ET Adman, J Sand-ers-Loehr. The environment of Ee4S4 clusters in ferredoxms and high-potential iron proteins. New information from X-ray crystallography and resonance Raman spectroscopy. J Am Chem Soc 113 2055-2064, 1991. 

Nonrepetitive but well-defined structures of this type form many important features of enzyme active sites. In some cases, a particular arrangement of coil structure providing a specific type of functional site recurs in several functionally related proteins. The peptide loop that binds iron-sulfur clusters in both ferredoxin and high potential iron protein is one example. Another is the central loop portion of the E—F hand structure that binds a calcium ion in several calcium-binding proteins, including calmodulin, carp parvalbumin, troponin C, and the intestinal calcium-binding protein. This loop, shown in Figure 6.26, connects two short a-helices. The calcium ion nestles into the pocket formed by this structure. 

Table 25.8 Reduction potentials of some iron proteins...

Figure 25.9 Some non-haem iron proteins (a) rubredoxin in which the single Fe is coordinated, almost tetra-hedrally, to 4 cysteine-sulfurs, (b) plant ferredoxin, [Fe2S2(S-Cys)4], (c) [Fe4S4(S-Cys)4] cube of bacterial ferredoxins. (This is in fact distorted, the Fe4 and S4 making up the two interpenetrating tetrahedra, of which the latter is larger than the former).

Biochemical aspects of Fe—S linkages in non-aqueous heme iron proteins with special reference to Andrenodoxin. T. Kimura, Struct. Bonding (Berlin), 1968, 5, 2-40 (72). 

Metal-polypeptide interactions the conformational state of iron proteins. M. Llinas. Struct. Bonding (Berlin), 1973, 17, 135-220 (320). 

Mossbauer studies on iron proteins. B. H. Huynh andT. A. Kent, Adv. Inorg. Biochem., 1984, 6, 164(178). 

Livorness J, Smith T (1982) The Role of Manganese in Photosynthesis. 48 1-44 Llinas M (1973) Metal-Polypeptide Interactions The Conformational State of Iron Proteins. 17 135-220... 

Rieske, J. S. In Nonheme Iron Proteins Role in Energy Conservation San Pietro, E., Ed. The Antioch Press Yellow Springs, OH, 1965, 461-468. 

Ruettinger RT, GR Griffith, MJ Coon (1977) Characteristics of the u-hydroxylase of Pseudomonas oleovorans as a non-heme iron protein. Arch Biochem Biophys 183 528-537. 

Yamamoto I, T Saiki, S-M Liu, LG Ljungdahl (1983) Purification and properties of NADP-dependent formate dehydrogenase from Clostridium thermoaceticum, a tungsten-selenium-iron protein. J Biol Chem 258 1826-1832. 

Kimura, T. Biochemical Aspects of Iron Sulfur Linkage in None-Heme Iron Protein, with Special Reference to Adrenodoxin . Vol. 5, pp. 1-40. 

Llinas, M. Metal-Polypeptide Interactions The Confirmational State of Iron Proteins. Vol. 17, pp. 135-220. 

The general influence of covalency can be qualitatively explained in a very basic MO scheme. For example, we may consider the p-oxo Fe(III) dimers that are encountered in inorganic complexes and nonheme iron proteins, such as ribonucleotide reductase. In spite of a half-filled crystal-field model), the ferric high-spin ions show quadrupole splittings as large as 2.45 mm s < 0, 5 = 0.53 mm s 4.2-77 K) [61, 62]. This is explained... 

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