Cytochrome interaction between

Electron Transport Between Photosystem I and Photosystem II Inhibitors. The interaction between PSI and PSII reaction centers (Fig. 1) depends on the thermodynamically favored transfer of electrons from low redox potential carriers to carriers of higher redox potential. This process serves to communicate reducing equivalents between the two photosystem complexes. Photosynthetic and respiratory membranes of both eukaryotes and prokaryotes contain stmctures that serve to oxidize low potential quinols while reducing high potential metaHoproteins (40). In plant thylakoid membranes, this complex is usually referred to as the cytochrome b /f complex, or plastoquinolplastocyanin oxidoreductase, which oxidizes plastoquinol reduced in PSII and reduces plastocyanin oxidized in PSI (25,41). Some diphenyl ethers, eg, 2,4-dinitrophenyl 2 -iodo-3 -methyl-4 -nitro-6 -isopropylphenyl ether [69311-70-2] (DNP-INT), and the quinone analogues,... 

Both attractive forces and repulsive forces are included in van der Waals interactions. The attractive forces are due primarily to instantaneous dipole-induced dipole interactions that arise because of fluctuations in the electron charge distributions of adjacent nonbonded atoms. Individual van der Waals interactions are weak ones (with stabilization energies of 4.0 to 1.2 kj/mol), but many such interactions occur in a typical protein, and, by sheer force of numbers, they can represent a significant contribution to the stability of a protein. Peter Privalov and George Makhatadze have shown that, for pancreatic ribonuclease A, hen egg white lysozyme, horse heart cytochrome c, and sperm whale myoglobin, van der Waals interactions between tightly packed groups in the interior of the protein are a major contribution to protein stability. 

When the second-site revertants were segregated from the original mutations, the bci complexes carrying a single mutation in the linker region of the Rieske protein had steady-state activities of 70-100% of wild-type levels and cytochrome b reduction rates that were approximately half that of the wild type. In all these mutants, the redox potential of the Rieske cluster was increased by about 70 mV compared to the wild type (51). Since the mutations are in residues that are in the flexible linker, at least 27 A away from the cluster, it is extremely unlikely that any of the mutations would have a direct effect on the redox potential of the cluster that would be observed in the water-soluble fragments. However, the mutations in the flexible linker will affect the mobility of the Rieske protein. Therefore, the effect of the mutations described is due to the interaction between the positional state of the Rieske protein and its electrochemical properties (i.e., the redox potential of the cluster). 

Y. Sallez, P. Bianco, and E. Lojou, Electrochemical behavior of c-type cytochromes at clay-modified carbon electrodes a model for the interaction between proteins and soils. J. Electroanal. Chem. 493, 37-49 (2000). 

In one series of experiments the cytochrome c oxidase mutations replaced acidic residues by neutral ones, and some of them were thus expected to alter the nature of binding of the protein to cytochrome c. From the pattern of dependence of the heme c to Cua electron-transfer rate constant on these mutations it was deduced that the binding of cytochrome c to cytochrome c oxidase is mediated by electrostatic interactions between four specific acidic residues on cytochrome c oxidase and lysines on cytochrome c. In another series of experiments, tryptophan 143 of cytochrome c oxidase was mutated to Phe or Ala. These mutations had an insignificant effect on the binding of the two proteins, but they dramatically reduced the rate constant for electron transfer from heme c to Cua- It was concluded that electron transfer from... 

Nakanishi, A., Imajoh-Ohmi, S., Fujinawa, T., Kikuchi, H., Kanegasaki, S. (1992). Direct evidence for interaction between COOH-terminal regions of cytochrome bssg subunits and cytosolic 47-kDa protein during activation of an 02"-generating system in neutrophils. J. Biol. Chem. 267, 19072-4. 

H. Koloczek, T. Horie, T. Yonetani, H. Anni, G. Maniara, and J. M. Vanderkooi, Interaction between cytochrome c and cytochrome c peroxidase Excited-state reactions of zinc- and tin-substituted derivatives, Biochemistry 26, 3142-3148 (1987). 

E. Friere, T. Markello, C. Rigell, and P. W. Holloway, Calorimetric and fluorescence characterization of interactions between cytochrome bs and phosphatidylcholine bilayers, Biochemistry 22, 1675-1680 (1983). 

Shidoji, Y., Hayashi, K., Komura, S., Ohishi, N., and Yagj, K., 1999, Loss ofmolecular interaction between cytochrome c and cardiohpin due to lipid peroxidation, Biochem. Biophys. Res. Commun. 264 343-347. 

Interaction Between Cytochrome c and Oxidized Mitochondrial Lipids... 

In this chapter, we describe a molecular interaction between cytochrome c and cardiolipin which prevents peroxidation of the lipid, implying that cardiolipin may play an important role in determination of the fate of the cell. In other words, a peroxidation of cardiolipin may well allow cytochrome c to discharge from the mitochondrial inner membrane into the cytosoUc space during apoptotic ceU death. 

It is noteworthy that in om NMR experiment 0.1 M sodium phosphate buffer remarkably attenuated the interaction between cardiolipin and cytochrome c, indicating that electrostatic interactions between anionic... 

Figure 4. Computer simulation of the interaction between human cytochrome c and cardiolipin tetralinoleoyl (A) and a schematic drawing ( kendama model) of the interaction...

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