Projects per year
Abstract
The autotrophic Sideroxydans lithotrophicus ES-1 can grow by coupling the oxidation of ferrous iron to the reduction of oxygen. Soluble ferrous iron is oxidised at the surface of the cell by an MtoAB porin-cytochrome complex that functions as an electron conduit through the outer membrane. Electrons are then transported to the cytoplasmic membrane where they are used to generate proton motive force (for ATP synthesis) and NADH for autotrophic processes such as carbon fixation.
As part of the mtoAB gene cluster, S. lithotrophicus also contains the gene mtoD that is proposed to encode a cytochrome c protein. We isolated mtoD from a Shewanella oneidensis expression system where the mtoD gene was expressed on a pBAD plasmid vector. Biochemical, biophysical and crystallographic characterisation of the purified MtoD revealed it as an 11 kDa monomeric protein containing a single heme. Sequence and structural alignment indicated that MtoD belonged to the class-1 cytochrome c family and had a similar fold to ferricytochrome c552 family, however the MtoD heme is bis-histidine coordinated and is substantially more exposed than the hemes of other family members. The reduction potential of the MtoD heme at pH 7 was +155 mV vs. Standard Hydrogen Electrode, which is approximately 100 mV lower than that of mitochondrial cytochromes c. Consideration of the properties of MtoD in the context of the potential respiratory partners identified from the genome suggests that MtoD could associate to multiple electron transfer partners as the primary periplasmic electron shuttle.
As part of the mtoAB gene cluster, S. lithotrophicus also contains the gene mtoD that is proposed to encode a cytochrome c protein. We isolated mtoD from a Shewanella oneidensis expression system where the mtoD gene was expressed on a pBAD plasmid vector. Biochemical, biophysical and crystallographic characterisation of the purified MtoD revealed it as an 11 kDa monomeric protein containing a single heme. Sequence and structural alignment indicated that MtoD belonged to the class-1 cytochrome c family and had a similar fold to ferricytochrome c552 family, however the MtoD heme is bis-histidine coordinated and is substantially more exposed than the hemes of other family members. The reduction potential of the MtoD heme at pH 7 was +155 mV vs. Standard Hydrogen Electrode, which is approximately 100 mV lower than that of mitochondrial cytochromes c. Consideration of the properties of MtoD in the context of the potential respiratory partners identified from the genome suggests that MtoD could associate to multiple electron transfer partners as the primary periplasmic electron shuttle.
Original language | English |
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Article number | 332 |
Journal | Frontiers in Microbiology |
Volume | 6 |
DOIs | |
Publication status | Published - 28 Apr 2015 |
Keywords
- MtoD
- cytochrome
- sideroxydans lithotropicus
- iron oxidation
Profiles
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Julea Butt
- School of Biological Sciences - Professor of Biophysical Chemistry
- Centre for Molecular and Structural Biochemistry - Member
- Centre for Photonics and Quantum Science - Member
- Chemistry of Life Processes - Member
- Chemistry of Light and Energy - Member
- Energy Materials Laboratory - Member
- Molecular Microbiology - Member
Person: Research Group Member, Research Centre Member, Academic, Teaching & Research
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Tom Clarke
- School of Biological Sciences - Professor
- Centre for Molecular and Structural Biochemistry - Member
- Energy Materials Laboratory - Member
- Molecular Microbiology - Member
Person: Research Group Member, Research Centre Member, Academic, Teaching & Research
Projects
- 2 Finished
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Molecular Basis for Controlled Transmembrane Electron Transfer
Clarke, T., Butt, J. & Richardson, D.
Biotechnology and Biological Sciences Research Council
1/01/13 → 31/12/15
Project: Research