Structural and functional studies of multiheme cytochromes C involved in extracellular electron transport in bacterial dissimilatory metal reduction

Bacteria utilizing insoluble mineral forms of metal oxides as electron acceptors in respiratory processes are widespread in the nature. The electron transfer from a pool of reduced quinones in the cytoplasmic membrane across the periplasm to the bacterial outer membrane and then to an extracellular acceptor is a key step in bacterial dissimilatory metal reduction. Multiheme cytochromes c play a crucial role in the extracellular electron transfer. The bacterium Shewanella oneidensis MR-1 was used as a model organism to study the mechanism of extracellular electron transport. In this review, we discuss recent data on the composition, structures, and functions of multiheme cytochromes c and their functional complexes responsible for extracellular electron transport in Shewanella oneidensis.