Photoinduced Electron-Transfer Reactions of Plastocyanin with the Triplet State of Zinc Myoglobin and with the Zinc Myoglobin Cation Radical. Protein-Protein Orientation in the Absence of Strong Electrostatic Interactions

Abstract

Various redox properties and electron-transfer reactions of myoglobin have been studied, but very few of these studies have dealt with reactions between myoglobin and other redox proteins. We report kinetics of two such photoinduced bimolecular reactions-reduction of cupriplastocyanin by the triplet state of zinc myoglobin (the forward reaction) and oxidation of cuproplastocyanin by the cation radical of zinc myoglobin (the back reaction). A widely-used version of Debye-Huckel theory reproduces the dependence on ionic strength of the forward reaction but not of the back reaction