Iron consensus

The conversion of a [3Fe-4S] into a [4Fe-4S] center was achieved by restoring the second residue of the consensus motif in E. coli fu-marate reductase (181) and in D. africanus ferredoxin III (161). However, the coordination scheme of the iron-sulfur centers of A. vinelan-... 

The Fur protein from E. coli was isolated in one step due to its high affinity for metal-chelate columns loaded with zinc. In DNase footprinting experiments, the Fur protein was shown to bind DNA in the promoter region of several iron-regulated genes. The consensus sequence, called the Fur box, is GATAATGATAATCATT ATC. In vitro binding is dependent on the divalent cations Co2+ Mn2+ /s Cd2+ Cu2+ at 150 iM, while Fe2+ seemed to be less active at this concentration, probably due to oxidation to Fe3+ (De Lorenzo et al., 1987). The unspecificity for divalent metals observed in vitro shows that the cells have to select the ions transported carefully and have to balance their active concentrations. In addition, it is a caveat for the experimenter to test a hypothesis on metal-ion specificity not only in vitro, but also in vivo. 

For a precipitated iron catalyst, several authors propose that the WGS reaction occurs on an iron oxide (magnetite) surface,1213 and there are also some reports that the FT reaction occurs on a carbide surface.14 There seems to be a general consensus that the FT and WGS reactions occur on different active sites,13 and some strong evidence indicates that iron carbide is active for the FT reaction and that an iron oxide is active for the WGS reaction,15 and this is the process we propose in this report. The most widely accepted mechanism for the FT reaction is surface polymerization on a carbide surface by CH2 insertion.16 The most widely accepted mechanism for the WGS reaction is the direct oxidation of CO with surface 0 (from water dissociation).17 Analysis done on a precipitated iron catalyst using bulk characterization techniques always shows iron oxides and iron carbides, and the question of whether there can be a sensible correlation made between the bulk composition and activity or selectivity is still a contentious issue.18... 

Ferredoxins (Fds) are widespread in the three domains of life and an abundance of sequence data and structural information are available for Fds isolated from several sources. In particular, the bacterial type Fds are small electron-transfer proteins that posses cubane xFe-yS clusters attached to the protein matrix by Fe ligation of Cys via a conserved consensus ligating sequence. The archaeal type ferredoxins are water-soluble electron acceptors for the acyl-coenzyme A forming 2-oxoacid/ferredoxin oxidoreductase, a key enzyme involved in the central archaeal metabolic pathways. Fds have been distinguished according to the number of iron and inorganic sulphur atoms, 2Fe-2S, 4Fe-4S/3Fe-4S (Fig. Ib-d) and Zn-containing Fds. 

Manoguerra AS, Erdman AR, Booze LL, Christianson G, Wax PM, Scharman EJ et al. Iron ingestion an evidence-based consensus guideline for out-of-hospital management. Clin Toxicol 2005 43 553-70. 

Psychotropic medication use is associated more with causing difficulties with eating rather than as a treatment for eating disorders. None of the medications investigated in the treatment of primary anorexia nervosa have been shown to be efficacious. Pica is defined as the eating of non-food substances. In the Expert Consensus survey (Rush and Frances, 2000) 63% of the respondents stated that no medication treatment is indicated for this disorder. Should medication be considered, then SSRI medications were most commonly endorsed. Another alternative is treatment with mineral or nutritional supplements, such as zinc or iron. 

Iron-sulfur clusters are important co-factors in electron-transfer. Type I reaction centres contain [4Fe-4S] clusters as final electron acceptors mediating ET to soluble electron carriers like ferredoxin or flavodoxin (reviewed in references 188, 224, 314, 315) In PS I three clusters (F FA and FB) have been clearly identified and spectroscopically characterized. The PsaA and PsaB subunits carry most of the ET cofactors in PS I.18178-316 Each of them provides two Cys ligands to the binding site of the interpolypeptide [4Fe-4S] cluster Fx. This binding site is identical on both core PS I subunits.317 Both [4Fe-4S] clusters FA and Fb are bound to the PS I stromal subunit PsaC. It contains two identical [4Fe-4S] consensus binding sites CxxCxxCxxxCP (C = cysteine, P = proline). 

The unique spectra of either Aj or Aj- could be detected in unbound PsaC where cysteine II in the consensus iron-sulfur binding site was changed to Asp, Gly, Ala, 88 314324. in this case the altered cluster is suggested to be in a high spin state (S > 3/2) and is therefore not detectable in the g = 2 region of the EPR spectra, where pure spectra of unchanged iron sulfur clusters in a low spin state (S = 1/2) could be observed. The unique spectra of FA- and FB could also be observed in the fully assembled PS I, which was dark-frozen in the presence of ascorbate and illuminated under cryogenic temperatures inside the EPR cavity (for review see reference 188). 

Extensive investigations on the catalytic mechanism of classical peroxidases resulted in a consensus model involving five different iron species [30, 31], These species are ferrous, ferric, Compound I, Compound II, and Compound III (Fig. 11.1). As discussed in Chap. 5, after the reaction of ground state (GS) Femporphyrin with H202, Compound I (Cl) is formed, a cationic oxob e,vpor-phyrin-based Ji-free radical. Electron paramagnetic resonance (EPR) studies established that, in peroxidases of classes I and III, the second oxidation equivalent in Cl is present as a porphyrin-based free radical [32, 33]. In peroxidases from fungal sources, electron abstraction from the protein results in the formation of a different species with the free radical based in a residue close to the porphyrin. 

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