Ferrocytochrome structures

Recently, Sivakolundu and Mabrouk published an NMR solution structure of horse heart ferrocytochrome c in which the heme contains an Fe(II) ion. This solution structure was the first in which the cytochrome c protein was dissolved in a nonaqueous solvent a solvent mix of 70% water and 30% acetonitrile (ACN). The data obtained from the NMR study are deposited in the protein data bank (PDB) as (1) ILCl, the minimized average NMR structure and (2) 1LC2, the 30 lowest energy NMR structures. 

Ihkano T, Dickerson RE (1981) Conformation change of cytochrome c. I. Ferrocytochrome c structure refined at 1.5 A resolution. J Mol Biol 153 79-94... 

A comparative study of the metal centers in cytochrome c oxidase from several bacterial sources, including Thermus thermophilus and P. denitrificans, using EPR and MCD spectroscopy has established that in both cases cytochrome a is liganded by two histidine oxidases and the Cua center is identical to that in bovine cytochrome c oxidase (105, 106). The properties of the cytochrome Os/Cub dimer have not been established to be identical, although ferrocytochrome 03 is high-spin ferrous, as expected. Recent studies of the MCD properties of the Cua center in cytochrome c oxidase and a copper center in nitrous oxide reductase (107,108) show that the two centers are virtually identical. The evidence from the EPR hyperfine structure of the copper center in nitrous oxide reductase suggests that the center in this enzyme is a mixed-valence Cu(I)/Cu(II) dimer, which raises the interesting prospect that the Cua center in cytochrome c oxidase is also a dimeric copper species. 

This is usually isolated from yeast, and has a molecular weight of 53 000 with one heme b. It catalyzes the oxidation of ferrocytochrome c by hydrogen peroxide. It is the first peroxidase for which the structure has been determined. The imidazole axial ligand is His-174, while Arg-48, Trp-51 and His-52 provide distal catalytic groups. The mechanism involves nucleophilic attack of peroxide on the Fe, loss of the ROOH proton to the imidazole of His-52, and transfer of this proton to the leaving RO group. Compound I of cytochrome c peroxidase is red, and differs from HRPI in that the additional oxidizing equivalent is on a protein residue. ESR and ENDOR spectra have been interpreted in terms of a methionine-centred free radical. One possibility is that a ferryl porphyrin cation radical is formed with cytochrome c peroxidase (it is attractive to assume that this would be common to all peroxidases), but that cytochrome c peroxidase has a readily oxidizable substrate which reduces the porphyrin radical. ... 

For the complete structures of ferrocytochrome c (Fe- ). see Takano, T. Trus, B. L. Mandel. N. Mantlet, G. Kallai, O. B. Swan.son, R. Dickerson. R. E. J. Biol. Chem. 1977, 252. 776-785. Sec Stryer. L. Biochemistry, 3rd cd. Freeman New York, 1981 pp 328-329. Dickerson, R. E. Sci. Amer. 1972, 226(4) pp 58-72. Eucaryotic cells have their DNA in true nuclei, as opposed to procaryotic cells (bacteria and blue-green algae) which do not. u The prefix met- is used to signify that the iron atom, normally in the -I-2 oxidation state, has been oxidized to -t-3. 

Cytochrome having hemes O and B is known as cytochrome bo3 (or bo). This cytochrome functions as the terminal oxidase in many bacteria. It resembles cytochrome aa3 in structure heme O and Cub of the cytochrome compose the dimetallic center to reduce molecular oxygen (Mogi et al., 1998). However, this cytochrome does not utilize ferrocytochrome c as the electron donor. The electron donor for cytochrome bo3 is ubiquinol it is an ubiquinol oxidase. Moreover, it shows proton pumping activity. 

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