Electron transfer proteins reduction potentials

It is also essential that any functional properties of the mutant protein that can be assessed be assessed. Although the substitution of one particular residue for another may be made in an attempt to determine the effect of the mutation on a specific property of a protein, it is quite possible that other properties that are not of immediate concern may be modified unintentionally and that these modifications may have important, otherwise occult, implications for the functional studies that are of immediate interest (vide infra). In the case of electron transfer proteins it may be useful, for example, to produce a family of mutants the members of which differ from each other only in their reduction potentials. This result may prove to be difficult to achieve because many mutations that perturb the reduction potential of a protein may also change its electrostatic properties or its reorganizational barrier to electron transfer. Depending on the experiments to be conducted with the mutants, these other properties may prove to be more important considerations than the reduction potentials of the mutants. In summary, new mutant proteins are ideally studied as if they were altogether new proteins of the same general class as the wild-type protein, and assumptions regarding the properties of such mutants should be kept to a minimum. 

The kinetics of oxidation and reduction of [4Fe-4S] proteins by transition metal complexes and by other electron-transfer proteins have been studied. These reactions do not correlate with their redox potentials.782 The charge on the cluster is distributed on the surface of HiPIP through the hydrogen bond network, and so affects the electrostatic interaction between protein and redox agents such as ferricyanide, Co111 and Mnin complexes.782 783 In some cases, limiting kinetics were observed, showing the presence of association prior to electron transfer.783... 

The reduction potential is central for the function of electron-transfer proteins, since it determines the driving force of the reaction. In particular, it must be poised between the reduction potentials of the donor and acceptor species. Therefore, electron-transfer proteins normally have to modulate the reduction potential of the redox-active group. This is very evident for the blue copper proteins, which show reduction potentials ranging from 184 mV for stellacyanin to 1000 mV for the type 1 copper site in domain 2 of ceruloplasmin [1,110,111]. 

HiPIP Formerly used abbreviation for high-potential iron-sulfur protein, now classed as a ferredoxin. An ELECTRON-TRANSFER PROTEIN from photosynthetic and other bacteria, containing a [4FE-4S] CLUSTER which undergoes oxidation-reduction between the [4Fe-4S]2+ and [4Fe-4S]3+ states. 

Determinants of the Reduction Potential in RubredoxinSy the Simplest Iron-Sulfur Electron-transfer Proteins... 

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