Optical and magneto-optical activity of cytochrome bd from Geobacillus thermodenitrificans
| Autor: | Mai Inadome, Vitaliy B. Borisov, Junshi Sakamoto, Alexander M. Arutyunyan, Yoshiki Kabashima |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Circular dichroism
Enzyme complex Cytochrome Stereochemistry Biophysics Heme medicine.disease_cause Biochemistry Thermophilic bacterium chemistry.chemical_compound Magnetics medicine Chlorin Escherichia coli Spectroscopy Oxidase test biology Circular Dichroism Escherichia coli Proteins Geobacillus Cell Biology Cytochrome b Group Porphyrin Heme B Metabolism chemistry Electron Transport Chain Complex Proteins Excitonic coupling biology.protein Molecular bioenergetics Cytochromes Oxidoreductases |
| Zdroj: | Biochimica et biophysica acta. 1817(11) |
| ISSN: | 0006-3002 |
| Popis: | Cytochromes bd are terminal oxidases in the respiratory chains of many prokaryotic organisms. They reduce O₂ to 2H₂O at the expense of electrons extracted from quinol. The oxidases can be divided into two subfamilies, L and S, based on the presence of either a long or a short hydrophilic connection between transmembrane helices 6 and 7 in subunit I designated as 'Q-loop'. The L-subfamily members, e.g. the enzyme from Escherichia coli, are relatively well-studied and were shown to generate proton-motive force. The S-subfamily comprises the majority of cytochromes bd including the enzyme from Geobacillus thermodenitrificans but is very poor studied. We compared the properties of cytochromes bd from G. thermodenitrificans and E. coli at room temperature using a combination of absorption, CD and MCD spectroscopy. The G. thermodenitrificans enzyme does contain the high-spin heme b(HS) ("b(595)") despite the fact that its characteristic Q(00)-band ("α"-band) at 595nm is not seen in the absorption spectra; stoichiometry of hemes b(LS), b(HS) and d per the enzyme complex is suggested to be 1:1:1. At 1mM CO, 20-25% of ferrous heme b(HS) in the G. thermodenitrificans oxidase binds the ligand, while in case of the E. coli enzyme such a reaction is minor. In the G. thermodenitrificans oxidase, the excitonic interaction between ferrous hemes b(HS) and d decreased as compared to that in the E. coli bd. The latter may suggest that the two enzymes differ in the distance between heme d and heme b(HS) and/or in the angle between their porphyrin planes. |
| Databáze: | OpenAIRE |
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