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Charge transfer between tryptophan and tyrosine in proteins


, : Charge transfer between tryptophan and tyrosine in proteins. Biochimica et Biophysica Acta 705(2): 150-162

With numerous proteins, most of which are not involved in oxidation reduction reactions, azide radicals reacted with tryptophan units to give Trp radicals. The Trp. radicals commonly transfer their electron deficiencies to tyrosine with rate constants in the region of 102-104 s-1, producing TyrO. For .beta.-lactoglobulin, which was studied in most detail, the rate of transfer is independent of protein concentration, so the reaction must be intramolecular. Sodium perchlorate and SDS [sodium dodecyl sulfate] affect the rate, probably because of alterations in protein conformation. The activation energy for the process is 45 kJ .cntdot. mol-1, inconsistent with any mechanism involving H-bonds or charge conduction through the chain, but consistent with tunnelling. With other proteins there is evidence of intermolecular transfer as well as intramolecular transfer, and there may be several different intramolecular steps corresponding to different tryptophan-tyrosine pairs. Rates are not always the same as those initiated by photoionization of tryptophan, probably because different tryptophan units are involved. The possibility of transformation means that with enzymes the initial site of attack by free radicals is not necessarily the site responsible for any consequent loss in activity. The oxidation-reduction potentials involved in the transfer are such that the process may be important in the mode of action of enzymes such as high-potential Cu proteins and peroxidases, and perhaps also in the mode of other proteins if the environment is suitable.

Accession: 001053518

DOI: 10.1016/0167-4838(82)90173-x

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Related references

Butler, J.; Land, E.J.; Pr�tz, W.A.; Swallow, A.J.hn, 1986: Reversibility of charge transfer between tryptophan and tyrosine. Journal of the Chemical Society, Chemical Communications 4: 348

Reece, S.Y.; Stubbe, J.; Nocera, D.G., 2005: pH Dependence of charge transfer between tryptophan and tyrosine in dipeptides. Time-resolved absorption spectroscopy has been employed to study the directionality and rate of charge transfer in W-Y and Ac-W-Y dipeptides as a function of pH. Excitation with 266-nm nanosecond laser pulses produces both W. (or (.WH)+, depending...

Joshi, R.; Mukherjee, T., 2002: Charge transfer between tryptophan and tyrosine in casein: A pulse radiolysis study. Charge transfer from tyrosine to tryptophan radicals in bovine milk casein, as observed using pulse radiolysis technique, is reported. The reactions of casein with hydroxyl, azide, Br(2)(*-) and CCl(3)O(2)(*) radicals have also been studied. Radic...

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Bobrowski K.; Holcman J.; Wierzchowski K.L., 1989: Intramolecular charge transfer in model peptides and lysozyme involving tryptophan and tyrosine. Biophysical Journal 55(2 PART 2): 347A

Bobrowski, K.; Lubis, R., 1986: Intermolecular charge transfer involving tryptophan, tyrosine and three electron-bonded intermediates derived from methionine. Oxidation processes of radiation-generated three-electron-bonded intermediates derived from methionine Met2[S+...S] and Met[S...X] (X=Cl,Br) were investigated through reaction with tryptophan and tyrosine, using the optical pulse radiolysis method...

Prütz, W.A.; Land, E.J., 1979: Charge transfer in peptides. Pulse radiolysis investigation of one-electron reactions in dipeptides of tryptophan and tyrosine. One-electron oxidation of TyrOH-TrpH or TrpH-TyrOH in aqueous solutions by N3 radicals occurs predominantly at the tryptophyl residue. The corresponding indolyl radicals (absorbing at 510 nm) are subsequently transformed into phenoxyl radicals (ab...

Pruetz W.A.; Siebert F.; Butler J.; Land E.J.; Menez A.; Montenay Garestier T., 1982: Charge transfer in peptides intra molecular radical transformations involving methionine tryptophan and tyrosine. An efficient intramolecular transfer of electron deficiency from tryptophan (TrpH) to tyrosin (TyrOH) was observed in numerous synthetic and natural peptides in aqueous solutions. The transfer was initiated pulse radiolytically by azide radicals,...

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