Unfolded proteins cytochrome

Ahmad A, Madhusudanan KP, Bhakuni V (2000) Trichloroacetic acid and trifluoroacetic acid-induced unfolding of cytochrome c stabilization of a native-like folded intermediate. Biochim Biophys Acta Protein Struct Mol Enzymol 1480 201-210... 

The fraction of Us molecules depends on the number of proline residues and on their isomeric state in the native protein. In particular, the presence of cts-prolyl peptide bonds in the folded molecules leads to a high fraction of Us, since in unfolded proteins the cis state is populated to a small extent only. Adler and Scheraga (1990) showed by NMR that in heat-unfolded RNase A the nonnative trans isomers predominate at both Pro93 and Proll4. The Up molecules dominate in the unfolded state of proteins that have only tram-prolyl peptide bonds, such as lysozyme (Kato et ai, 1981, 1982), cytochrome c (Ridge el ai, 1981 Nall,... 

Figure 5. Extent of Protein Unfolding with MW. The unfolding kinetics are depicted here at 9 minutes of unfolding at room temperature for each of 4 proteins cytochrome c, bovine serum albumin, immunoglobulin G, and fibrinogen. The correlation coefficient (R ) for this curve was 0.97.

Szucs et alP studied both the adsorption and the mediated and unmediated electron transfer from cytochrome c on a gold electrode using ellipsometry and cyclic voltammetry. They found that the protein formed an irreversibly adsorbed layer that completely covered the electrode. The adsorbed cytochrome c was able to mediate the reduction of cytochrome c in solution via electron transfer through the unfolded protein layer. They did not observe oxidation of cytochrome c in the potassium phosphate... 

BIPY, 2-PYS and 2-PYCH behave as surface active agents, which provide a hydrophobic electrode surface and prevent partial unfolding of cytochrome c at the silver electrode. It is also interesting to note that the spin state of cytochrome c co-adsorbed with 4-BIPY is the mixture of the HS state, which corresponds to cytochrome c adsorbed on a bare silver electrode, and the LS state, which corresponds to the native protein. The formal potential of cytochrome c co-adsorbed with these surface modifiers is aboiut -0.15 V. The shift of the formal potential of adsorbed cytochrome c on a silver electrode at -0.3 V to that of cytochrome c co-... 

Privalov et al (1989) studied the unfolded forms of several globular proteins [ribonuclease A, hen egg white lysozyme, apomyoglobin (apoMb), cytochrome c, and staphylococcal nuclease]. Unfolding was induced by 6 M Gdm-HCl at 10°C, heating to 80°C, or by low pH at 10°C with cross-links cleaved (reduction and carboxamidomethylation or removal of heme). The unfolded forms showed CD spectra (Fig. 27)... 

Cytochrome c possesses three phyllogenetically-conserved proline residues that are presumably involved in the correct folding of the protein to form the native structure. The effects of substitutions at one of these sites, Pro-71 (Fig. 4), on the equilibrium and kinetics of yeast iso-2-cytochrome c unfolding have been studied by Nall and co-workers through comparison of the properties of a Thr... 

Fig. 14. Effects of temperature on the absorbance of hemopexin and the N-domain of hemopexin. The unfolding of hemopexin and N-domain in 25 mM sodium phosphate, pH 7.4, was examined using absorbance spectroscopy (N. Shipulina et al., unpublished). The second derivative UV absorbance spectra of the protein moieties were used to follow protein unfolding and the Soret and visible region spectra to monitor the integrity of the heme complexes, as done with cytochrome 6502 (166). The ferri-heme complex is more stable than the apo-protein moiety, but the is slightly lower than that assessed by DSC, indicating that changes in conformation occur before thermodynamic unfolding. Reduction causes a large decrease in heme-complex stabihty, which is proposed to be a major factor in heme release from hemopexin by its cell membrane receptor, and addition of 150 mM sodium chloride enhanced the stabihty of ah forms of hemopexin.

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