Projects per year
Abstract
Thiosulfate dehydrogenases (TsdA) are bidirectional bacterial di-heme enzymes that catalyze the interconversion of tetrathionate and thiosulfate at measurable rates in both directions. In contrast to our knowledge of TsdA activities, information on the redox properties in the absence of substrates is rather scant. To address this deficit, we combined magnetic circular dichroism (MCD) spectroscopy and protein film electrochemistry (PFE) in a study to resolve heme ligation and redox chemistry in two representative TsdAs. We examined the TsdAs from Campylobacter jejuni, a micro-aerobe human pathogen, and from the purple sulfur bacterium Allochromatium vinosum. In these organisms, the enzyme functions as a tetrathionate reductase and a thiosulfate oxidase respectively. The active site Heme 1 in both enzymes has His/Cys− ligation in the ferric and ferrous states and the midpoint potentials (Em) of the corresponding redox transformations are similar, −185 mV versus standard hydrogen electrode (SHE). However, fundamental differences are observed in the properties of the second, electron transferring, Heme 2. In C. jejuni TsdA Heme 2 has His/Met ligation and an Em of +172 mV. In A. vinosum TsdA, Heme 2 reduction triggers a switch from His/Lys ligation (Em, −129 mV) to His/Met (Em,+266 mV) but the rates of interconversion are such that His/Lys ligation would be retained during turnover. In summary, our findings have unambiguously assigned Em values to defined axial ligand sets in TsdAs, specified the rates of Heme 2 ligand exchange in the A. vinosum enzyme, and provided information relevant to describing their catalytic mechanism(s).
Original language | English |
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Pages (from-to) | 18002-18014 |
Number of pages | 13 |
Journal | Journal of Biological Chemistry |
Volume | 294 |
Issue number | 47 |
Early online date | 29 Aug 2019 |
DOIs | |
Publication status | Published - 22 Nov 2019 |
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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Myles Cheesman
- School of Chemistry, Pharmacy and Pharmacology - Lecturer
- Centre for Molecular and Structural Biochemistry - Member
- Chemistry of Life Processes - Member
- Chemistry of Light and Energy - Member
Person: Research Group Member, Research Centre Member, Academic, Teaching & Research
Projects
- 2 Finished
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Advancing Biotechnologies for Fuel Generation: Exploiting Transmembrane Cytochromes for Solar Energy Conversion
Butt, J., Clarke, T., Richardson, D. & Lyall, V.
Biotechnology and Biological Sciences Research Council
30/06/13 → 29/06/16
Project: Research