Electrochemical investigation of binding sites of plantacyanin: Blue, copper-containing protein of plants

The binding site structure of plantacyanin (plant blue Cu-protein) was studied using voltammetry at the electrodes modified with sulphur-containing compounds (thioglycolic acid, dipyridyl disulfide, cysteamine, beta-mercaptoethanol). The scanning of the functional groups of the modifying layer was used to reveal the most efficient modifications of the electrode and to determine the character of the binding groups of the protein. A comparison of the electron exchange characteristics of plantacyanin at the different electrodes with that of the other proteins of the known binding site structure (plastocyanin, cytochrome c, cytochrome c553, high potential ion-sulfur protein) was carried out. By means of this comparison and also using literary data about plantacyanin tertiary structure, the localization of the protein binding sites and their hydrophobicity were evaluated. Two poles was suggested to exist with a high permeability to electrons. One of these binding sites is of a high hydrophobicity (4.1-6.7 kJ mol(-1)). The other is hydrophilic and contains several charged amino groups. The problem of how to search the partners of plantacyanin in the electron transport chain was discussed.