Proteins electron transfer with

In order to probe these effects, a number of studies on the kinetics of electron transfer between small molecule redox reagents and proteins, as well as protein-protein electron transfer reactions, have been carried out (38-41). The studies on reactions of small molecules with electron transfer proteins have pointed to some specificity in the electron transfer process as a function of the nature of the ligands around the small molecule redox reagents, especially the hydrophobicity of these... 

The investigation on the use of molecules suitable for modifying the electrode surface so as to favour electron transfers with proteins (so-called promoters, which are non-redox active molecules and therefore unable to act as redox mediators) has determined that they must be bifunctional molecules X—V /—Y, in which X is a group able to... 

Steady state kinetics and protein-protein binding measurements have also been reported for the interaction of these mutant cytochromes with bovine heart cytochrome c oxidase [120]. The binding of cytochrome c variants to the oxidase occurred with increasing values of Kj in the order He (3 x 10 Mol L ) < Leu = Gly < wild-type < Tyr < Ser (3 x 10 molL ). Steady-state kinetic analysis indicated that the rate of electron transfer with cytochrome c oxidase increased in the order Ser < He < Gly < Leu < Tyr < wild-type, an order notably different from that observed for a related analysis of the oxidation of these mutants by cytochrome c peroxidase [85]. This difference in order of mutant turnover by the oxidase and peroxidase may arise from differences in the mode of interaction of the cytochrome with these two enzymes. 

This proposition is amply verified by Type I (Tl) copper proteins (37,62). Tl centers are involved in electron transfer with perhaps the most famous example being plastocyanin (Pc), a crucial part of photosynthesis, and the first Tl protein to be... 

Many of the reactions of the plastocyanins and azurins with other redox proteins follow Marcus behaviour.946 These reactions all show a single mechanism of electron transfer, with no kinetic selectivity and no specific interactions between the proteins. The notable exception to this behaviour is cytochrome / (c552), where a specific interaction occurs,934 appropriate for its natural redox partner. Equation (48) represents a probable sequence of electron carriers, although it is difficult to extrapolate conclusions to the membrane-bound proteins. 

The electrons are subsequently transferred to the MoFe or VFe protein one at a time. The rate of binding of the Fe protein to the MoFe protein has been estimated to occur with a rate constant, k > 5 X 107 dm3 mol-1 sec-1, which is close to the diffusion-controlled limit (72). The Fe protein-MoFe protein electron transfer is followed, when S2042- is the reductant, by the rate-determining dissociation of the two proteins. 

Perhaps two key points are emerging from the frenzied activity in protein electron transfer. First, it is clear that rapid electron transfer can occur over long distances in proteins. Furthermore, the rates of these reactions are generally consistent with expectations based on simple small molecule reactions. In particular it appears that proteins, like other polymers, may provide relatively high reorganization energies for electron transfer. 

Many proteins are exclusively involved in intra-protein electron transfer and typically function in ordered structures such as mitochondria. Under these circumstances, the redox-active centers are generally accessible on the outer surface of the protein. In contrast, the redox reactions catalyzed by oxidoreductases involve small molecules with the reaction involving two redox couples, i.e. the substrate and the co-factor or co-substrate. Because the catalytic center of the enzyme is often located... 

Miyashita, O. and Go, N. (2000) Reorganization energy of protein electron transfer reaction study with structural and frequency signature, J. Phys. Chem. 104, 7516-7521. 

The 2,6-dipicolinic acid complex [Co(dipic)2] has recently been used as a lipophilic oxidant to study electron transfer with cytochromes c and cssl and with the blue copper centre in stellacyanin, plastocyanin and azurin penetration of the complex towards the metal centre of the protein is thought to aid electron transfer.257,271... 

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