Electron tunneling properties of outer-membrane decaheme cytochromes from Shewanella oneidensis
In this report, we describe the characterization of two outer-membrane decaheme cytochromes OmcA and MtrC purified from the metal-reducing bacterium Shewanella oneidensis using scanning tunneling microscopy (STM) and tunneling spectroscopy (TS). OmcA and MtrC were solubilized with a common detergent and irreversibly bound to Au (111) substrates as self-assembled cytochrome films. X-ray photoelectron spectroscopy (XPS) verified that OmcA and MtrC were covalently bound to the Au surface via thiol bonds to cysteine residues. Initial STM images show that a layer of detergent covers and protects the cytochrome films. Temporary application of high bias voltage causes the detergent film to reorganize around the tip, opening a window for direct STM imaging of the cytochrome layer underneath. The STM apparent sizes of both OmcA and MtrC are 58 nanometers in diameter consistent with expectations from their molecular masses. Current-voltage TS over individual cytochromes showed that OmcA and MtrC have different abilities to mediate the tunneling current, reflecting differences in their electronic structures. The data suggest that the two cytochromes could have different roles in the electron transport chain during metal reduction.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 902041
- Report Number(s):
- PNNL-SA-48154; KP1504010
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 3 Vol. 71; ISSN GCACAK; ISSN 0016-7037
- Publisher:
- The Geochemical Society; The Meteoritical Society
- Country of Publication:
- United States
- Language:
- English
Similar Records
Mechanisms of Electron Transfer in Two Decaheme Cytochromes from a Metal-Reducing Bacterium
Specific Bonds between an Iron Oxide Surface and Outer Membrane Cytochromes MtrC and OmcA from Shewanella oneidensis MR-1