OmcS nanowires (Geobacter nanowires) are conductive

filament The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including: Astronomy * Galaxy filament, the largest known cosmic structures in the universe * Solar filament ...

s found in some species of bacteria, including ''

Geobacter sulfurreducens ''Geobacter sulfurreducens'' is a gram-negative metal and sulphur-reducing proteobacterium. It is rod-shaped, obligately anaerobic, non-fermentative, has flagellum and type four pili, and is closely related to ''Geobacter metallireducens''. ''G ...

'', where they catalyze the transfer of electrons. They are multi heme c-Type

cytochrome Cytochromes are redox-active proteins containing a heme, with a central Fe atom at its core, as a cofactor. They are involved in electron transport chain and redox catalysis. They are classified according to the type of heme and its mode of bin ...

s localized outside of the cell of some exoelectrogenic bacterial species, serving as mediator of extracellular electron transfer from cells to Fe(III) oxides and other extracellular electron acceptors. OmcS
3D structure
has a core of six low-spin bis-histidinyl hexacoordinated heme groups inside a sinusoidal filament ~5-7.4 nm in diameter, with 46.7 Å rise per subunit and 4.3 subunits per turn. The six-heme packing motif of OmcS is identical to that seen in a ~3 nm diameter cytochrome nanowire, OmcE
3D structure
, even though OmcE and OmcS share no sequence similarity. The OmcS gene can be one the most highly up-regulated genes in the ''Geobacter sulfurreducens'' KN400 strain when cultivated in a microbial fuel cell, as compared to the PCA strain, although a role for OmcS in electron transfer to electrodes has never been demonstrated.

References

Oxidoreductases {{enzyme-stub