Electrode assemblies composed of redox cascades from microbial respiratory electron transfer chains

Respiratory and photosynthetic electron transfer chains are dependent on vectorial electron transfer through a series of redox proteins. Examples include electron transfer from NapC to NapAB nitrate reductase in Paracoccus denitrificans and from CymA to Fcc₃ (flavocytochrome c₃) fumarate reductase in Shewanella oneidensis MR-1. In the present article, we demonstrate that graphite electrodes can serve as surfaces for the stepwise adsorption of NapC and NapAB, and the stepwise adsorption of CymA and Fcc₃. Aspects of the catalytic properties of these assemblies are different from those of NapAB and Fcc₃ adsorbed in isolation. We propose that this is due to the formation of NapC–NapAB and of CymA–Fcc₃ complexes that are capable of supporting vectorial electron transfer.