Cytochrome c surfaces

Fig. 2a-c. Stereodiagram of the yeast iso-1-cytochrome c surface, (a) Surface of the wild-type protein (b) surface of the Ser-82 mutant (c) surface of the Gly-82 mutant. (Modified from Refs. [123, 124])... 

Tetraphenylporphyrin-based Synthetic Receptors for Targeting the Cytochrome c Surface... 

A second point of interest is that the study of the cytochrome c surface using probes reveals multiple sites and possible movements on the surface. These sites and the surface diffusion make the discussion of docking likely to be difficult. 

Figure C3.2.5. Strongest tunnelling patliways between surface histidines and tire iron atom in cytochrome c. Steps in patliways are denoted by solid lines (covalent bonds), dashed lines (hydrogen bonds), and tlirough-space contacts (dotted lines). Electron transfer distance to His 72 is 5 A shorter tlian in His 66, yet tire two rates are approximately...

Cytochrome c, like UQ is a mobile electron carrier. It associates loosely with the inner mitochondrial membrane (in the intermembrane space on the cytosolic side of the inner membrane) to acquire electrons from the Fe-S-cyt C aggregate of Complex 111, and then it migrates along the membrane surface in the reduced state, carrying electrons to cytochrome c oxidase, the fourth complex of the electron transport chain. 

Another pathway is the L-glycerol 3-phosphate shuttle (Figure 11). Cytosolic dihydroxyacetone phosphate is reduced by NADFl to s.n-glycerol 3-phosphate, catalyzed by s,n-glycerol 3-phosphate dehydrogenase, and this is then oxidized by s,n-glycerol 3-phosphate ubiquinone oxidoreductase to dihydroxyacetone phosphate, which is a flavoprotein on the outer surface of the inner membrane. By this route electrons enter the respiratory chain.from cytosolic NADH at the level of complex III. Less well defined is the possibility that cytosolic NADH is oxidized by cytochrome bs reductase in the outer mitochondrial membrane and that electrons are transferred via cytochrome b5 in the endoplasmic reticulum to the respiratory chain at the level of cytochrome c (Fischer et al., 1985). 

Armstrong FA, Bond AM, Buchi FN, Hanmett A, Hill HAO, Lannon AM, Lettington OC, Zoski CG. 1993. Electrocatalytic reduction of hydrogen-peroxide at a stationary pyrol3ftic-graphite electrode surface in the presence of cytochrome-c peroxidase— A description based on a microelectrode array model for adsorbed enzyme molecules. Analyst 118 973-978. 

A trianionic zinc porphyrin anchored to a membrane by an imidazole link has been used to bind cytochrome c at the membrane surface. UV spectra confirmed the insertion of the zinc porphyrin into the phospholipid vesicle and was used to study surface association of cytochrome c. 

These researchers also described [93] the design and synthesis of iron(II) porphyrin dendrimers with triethylene glycol monomethyl, ether surface groups (e.g., 31) which render them soluble in a wide range of organic solvents and water. The potential difference between the first (1 FeCl) and second generation (2 FeCl) Fe-porphryin dendrimers was found to increase more in water than in dichloromethane (0.42 vs 0.08 V). This remarkable potential difference between 2 FeCl and 1 FeCl in water was comparable with that found between cytochrome c and a similarly ligated, more solvent-exposed cytochrome c heme model compound. 

The improvement of its activity and stability has been approach by the use of GE tools (see Refs. [398] and [399], respectively). A process drawback is the fact that the oxidation of hydrophobic compounds in an organic solvent becomes limited by substrate partition between the active site of the enzyme and the bulk solvent [398], To provide the biocatalyst soluble with a hydrophobic active site access, keeping its solubility in organic solvents, a double chemical modification on horse heart cytochrome c has been performed [400,401], First, to increase the active-site hydrophobicity, a methyl esterification on the heme propionates was performed. Then, polyethylene glycol (PEG) was used for a surface modification of the protein, yielding a protein-polymer conjugates that are soluble in organic solvents. 

The effect of pH on the protein adsorption on CMK-3 was also investigated [152], The monolayer adsorption capacities obtained under various pH conditions are plotted in Figure 4.12, where the maximum adsorption was observed in the pH region near the isoelectric point of lysozyme (pi of about 11). Near the isoelectric point, the net charges of the lysozyme molecule are minimized and would form the most compact assembly. A similar pH effect was also seen in the adsorption of cytochrome c on CM K-3. Although the nature of the surface of mesoporous silica and... 

The work of Eddowes and Hill and Taniguchi and co-workers opened up an extremely exciting prospect, the more as it appeared that the technique of surface modification could be extended to enzymes other than cytochrome c. However, to exploit this technology fully the mode of action of these... 

Reported applications of DST include the crosslinking of ubiquinone cytochrome C reductase (Smith et al., 1978), characterization of the cell surface receptor for colony-stimulating factor (Park et al., 1986), investigation of the Ca+2-, Mg+2-activated ATP of E. coli (Bragg and Hou, 1980), and characterization of human properdin polymers (Farries and Atkinson, 1989). 

K.V. Gobi and F. Mizutani, Efficient mediatorless superoxide sensors using cytochrome c-modified electrodes. Surface nano-organization for selectivity and controlled peroxidase activity. J. Electroanal. Chem. 484, 172-181 (2000). 

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