OmcS oxidoreductase

OmcS nanowires (Geobacter nanowires) are conductive filaments 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 of some exoelectrogenic bacterial species, serving as mediator of extracellular electron transfer from cells to Fe(III) oxides and other extracellular electron acceptors.[1]

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.[2][3]

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.[4]

References
  1. Qian, X; Mester, T; Morgado, L; Arakawa, T; Sharma, ML; Inoue, K; Joseph, C; Salgueiro, CA; Maroney, MJ; Lovley, DR (2011). "Biochemical characterization of purified OmcS, a c-type cytochrome required for insoluble Fe(III) reduction in Geobacter sulfurreducens". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1807 (4): 404–412. doi:10.1016/j.bbabio.2011.01.003. PMID 21236241.
  2. Wang; et al. (2022). "Cryo-EM structure of an extracellular Geobacter OmcE cytochrome filament reveals tetrahaem packing". Nature Microbiology. 7 (8): 1291–1300. doi:10.1038/s41564-022-01159-z. PMC 9357133. PMID 35798889.
  3. Wang; et al. (2019). "Structure of Microbial Nanowires Reveals Stacked Hemes that Transport Electrons over Micrometers". Cell. 177 (2): 361–369.e10. doi:10.1016/j.cell.2019.03.029. PMC 6720112. PMID 30951668.
  4. Butler; et al. (2012). "Comparative genomic analysis of Geobacter sulfurreducens KN400, a strain with enhanced capacity for extracellular electron transfer and electricity production". BMC Genomics. 13: 471. doi:10.1186/1471-2164-13-471. PMC 3495685. PMID 22967216.


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