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Gold electrodes were modified with short oligonucleotides in order to facilitate the electron transfer to the small redox protein cytochrome c. DNA immobilization was followed by impedance spectroscopy. The electron exchange was found to be quasi-reversible for both the protein in solution or adsorbed at the electrode surface. Variations of base sequence or structure (DNA-PNA hybrids) of the nucleic acid promoter layer did not significantly change the electron transfer rate constant which was in the range of 0.2–1×10^–2 cm/s. Cytochrome c adsorbed at low ionic strength was coupled to molecules in solution such as superoxide or laccase. Aspects of the DNA conductivity and possibilities for DNA detection are also discussed.