A 300-fold conductivity increase in microbial cytochrome nanowires due to temperature-induced restructuring of hydrogen bonding networks.

Although proteins are considered as nonconductors that transfer electrons only up to 1 to 2 nanometers via tunneling, transports respiratory electrons over micrometers, to insoluble acceptors or syntrophic partner cells, via nanowires composed of polymerized cytochrome OmcS. However, the mechanism enabling this long-range conduction is unclear. Here, we demonstrate that individual nanowires exhibit theoretically predicted hopping conductance, at rate (>10 s) comparable to synthetic molecular wires, with negligible carrier loss over micrometers.

Structure of Geobacter pili reveals secretory rather than nanowire behaviour.

Extracellular electron transfer by Geobacter species through surface appendages known as microbial nanowires is important in a range of globally important environmental phenomena, as well as for applications in bio-remediation, bioenergy, biofuels and bioelectronics. Since 2005, these nanowires have been thought to be type 4 pili composed solely of the PilA-N protein. However, previous structural analyses have demonstrated that, during extracellular electron transfer, cells do not produce pili but rather nanowires made up of the cytochromes OmcS and OmcZ.

Intrinsic electronic conductivity of individual atomically resolved amyloid crystals reveals micrometer-long hole hopping via tyrosines.

Proteins are commonly known to transfer electrons over distances limited to a few nanometers. However, many biological processes require electron transport over far longer distances. For example, soil and sediment bacteria transport electrons, over hundreds of micrometers to even centimeters, via putative filamentous proteins rich in aromatic residues.

Electric field stimulates production of highly conductive microbial OmcZ nanowires.

Multifunctional living materials are attractive due to their powerful ability to self-repair and replicate. However, most natural materials lack electronic functionality. Here we show that an electric field, applied to electricity-producing Geobacter sulfurreducens biofilms, stimulates production of cytochrome OmcZ nanowires with 1,000-fold higher conductivity (30 S cm) and threefold higher stiffness (1.

Structure of the cytochrome -600 heme-copper menaquinol oxidase bound to inhibitor HQNO shows TM0 is part of the quinol binding site.

Virtually all proton-pumping terminal respiratory oxygen reductases are members of the heme-copper oxidoreductase superfamily. Most of these enzymes use reduced cytochrome as a source of electrons, but a group of enzymes have evolved to directly oxidize membrane-bound quinols, usually menaquinol or ubiquinol. All of the quinol oxidases have an additional transmembrane helix (TM0) in subunit I that is not present in the related cytochrome oxidases.

The Ubiquinol Binding Site of Cytochrome from Accommodates Menaquinone and Stabilizes a Functional Menasemiquinone.

Cytochrome , one of three terminal oxygen reductases in the aerobic respiratory chain of , has been well characterized as a ubiquinol oxidase. The ability of cytochrome to catalyze the two-electron oxidation of ubiquinol-8 requires the enzyme to stabilize the one-electron oxidized ubisemiquinone species that is a transient intermediate in the reaction. Cytochrome has been shown recently to also utilize demethylmenaquinol-8 as a substrate that, along with menaquinol-8, replaces ubiquinol-8 when is grown under microaerobic or anaerobic conditions.

Structure of Microbial Nanowires Reveals Stacked Hemes that Transport Electrons over Micrometers.

Long-range (>10 μm) transport of electrons along networks of Geobacter sulfurreducens protein filaments, known as microbial nanowires, has been invoked to explain a wide range of globally important redox phenomena. These nanowires were previously thought to be type IV pili composed of PilA protein. Here, we report a 3.

Plasticity in the High Affinity Menaquinone Binding Site of the Cytochrome aa3-600 Menaquinol Oxidase from Bacillus subtilis.

Cytochrome aa3-600 is a terminal oxidase in the electron transport pathway that contributes to the electrochemical membrane potential by actively pumping protons. A notable feature of this enzyme complex is that it uses menaquinol as its electron donor instead of cytochrome c when it reduces dioxygen to water. The enzyme stabilizes a menasemiquinone radical (SQ) at a high affinity site that is important for catalysis.

Characterization of the semiquinone radical stabilized by the cytochrome aa3-600 menaquinol oxidase of Bacillus subtilis.

Cytochrome aa(3)-600 is one of the principle respiratory oxidases from Bacillus subtilis and is a member of the heme-copper superfamily of oxygen reductases. This enzyme catalyzes the two-electron oxidation of menaquinol and the four-electron reduction of O(2) to 2H(2)O. Cytochrome aa(3)-600 is of interest because it is a very close homologue of the cytochrome bo(3) ubiquinol oxidase from Escherichia coli, except that it uses menaquinol instead of ubiquinol as a substrate.