Investigation of the Key Heme in Cytchrome c₃ to the Electron Pool Effect by Highly Sensitive EQCM Technique

Abstract

Cytochrome c₃, which has four bis-histidinyl coordinated hemes per molecule, is a redox protein, and stores electrons temporarily until recognizing a redox partner. This mechanism is called “electron pool effect”. In this study, highly sensitive EQCM measurement clarified which heme in cytochrome c₃ caused the electron pool effect. To investigate the key heme to the electron pool effect, cytochrome c₃ mutants in which the sixth axial ligand of one heme was changed were prepared, and the intermolecular electron transfer was measured by viologen-immobilized electrode. The kinetics of the electron transfer complex formation between cytochrome c₃ and immobilized viologen indicated that redox of the heme II in cytochrome c₃ caused the electron pool effect.