OmcS oxidoreductase

OmcS oxidoreductase (Geobacter nanowire, G-NET) are enzymes found in some species of bacteria, including "Geobacter sulfurreducens", where they catalyze the transfer of electrons. They are multiheme c-Type cytochromes localized outside of the cell along the pili of some exoelectrogenic bacterial species, serving as mediator of extracellular electron transfer from pili to Fe(III) oxides and other extracellular electron acceptors. 
OmcS may also facilitate temporary electron storage, acting as capacitor, allowing "Geobacter" species to move towards distant terminal electron acceptors.
OmcS has six low-spin bis-histidinyl hexacoordinated heme groups, and the OmcS gene is the most highly up-regulated of all genes in the "Geobacter sulfurreducens" KN400 strain when cultivated in a microbial fuel cell, as compared to the PCA strain.