Cytochrome anion binding

General anion binding site [Gd(dipic)3], [Cr(CN)J"-, [Cr(oxalate)3], and EDTA complexes of above cations Cytochrome-c ... 

Concur, D. W., Hill, H. A. O., Moore, G. R., Whitford, D., Williams, R. J. P., The Modulation of Cytochrome C Electron Self-Exchange by Site-Specific Chemical Modification and Anion Binding , FEBS Utt. 206 (1986) 15-19. 

A STUDY OF THE EFFECTS OF IONIC STRENGTH AND ANION BINDING ON THE REDUCTION POTENTIAL OF CYTOCHROME c USING MICROELECTRODES... 

A Study of the Effects of Ionic Strength and Anion Binding on the Reduction Potential of Cytochrome c Using Microelectrodes... 

Nevertheless, we know40 that cytochrome c in its two oxidation states has a different solubility, a different rate of movement on columns, and a different pH and temperature stability. It is also known that the protein binds anions (even chloride) or cations, or even other proteins differently on change of redox state. These binding differences would be sufficient to operate a relay. 

In the case of cytochrome c, these electrostatic terms are due to changes in the redox states of the internally bound protein metal ion. In other cases where the charges on anions or cations are numerically fixed, the ions can dissociate (e.g., as the metal ion leaves the protein) or migrate (e.g., Na% K+, Ca2+, Cl-, HPO2, H+). If the exchange of these ions involves sites, especially hydrophobic sites, deep inside proteins, on the one hand, and free solution or surface sites, on the other hand, then they will be expected to have an electrostatic influence on the protein much as in a change of redox state. Thus we look next at two calcium binding proteins and later at insulin. 

Germain, M., Mathai, J. P., and Shore, G. C., 2002, BH-3-only BIK functions at the endoplasmic reticulum to stimulate cytochrome c release from mitochondria, J. Biol. Chem. 277, pp. 18053—18060 Gincel, D., Zaid, H., and Shoshan-Barmatz, V., 2001, Calcium binding and translocation by the voltage-dependent anion channel a possible regulatory mechanism in mitochondrial function, Biochem. J. 358, pp. 147-155... 

Reaction of Cytochrome cIinn with Bis(ferrozine)copper(II) Knowledge of the redox properties of cytochrome c was an encouragement to initiate a kinetics investigation of the reduction of an unusual copper(II) complex species by cyt c11. Ferrozine (5,6-bis(4-sulphonatophenyl)-3-(2-pyridyl)-1,2.4-triazine)286 (see Scheme 7.1), a ligand that had come to prominence as a sensitive spectrophotometric probe for the presence of aqua-Fe(II),19c,287 forms a bis complex with Cu(II) that is square pyramidal, with a water molecule in a fifth axial position, whereas the bis-ferrozine complex of Cu(I) is tetrahedral.286 These geometries are based primarily upon analysis of the UV/visible spectrum. Both complexes are anionic, as for the tris-oxalato complex of cobalt in reaction with cytochrome c (Section 7.3.3.4), the expectation is that the two partners will bind sufficiently strongly in the precursor complex to allow separation of the precursor formation constant from the electron transfer rate constant, from the empirical kinetic data. 

The iron atom in haems and haemoproteins is usually five- or six-coordi-ftate, since it can bind ligands at the axial positions. Haems such as tron(II) protoporphyrin IX will readily coordinate neutral bases such as NHj and pyridine, small unsaturated molecules like CO, and some anions. In haemoproteins, at least one of the axial ligands is provided by the polypeptide, and with the exception of some cytochromes, this is the only linkage between the polypeptide and the prosthetic group. Where only We axial position is occupied by the polypeptide, the other is thought to be taken up by a water molecule in ferric haemoproteins. This is readily replaced by other ligands. Ferrous haemoproteins, in the absence of potential ligands such as CO, can remain five-coordinate. 

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