Abstract
Heliobacteria have a Rieske/cytochrome b complex composed of a Rieske protein, a cytochrome b(6,) a subunit IV and a di-heme cytochrome c. The overall structure of the complex seems close to the b(6)f complex from cyanobacteria and chloroplasts to the exception of the di-heme cytochrome. We show here by biochemical and biophysical studies that a heme c(i) is covalently attached to the Rieske/cytochrome b complex from Heliobacteria. We studied the EPR signature of this heme in two different species, Heliobacterium modesticaldum and Heliobacillus mobilis. In contrast to the case of b(6)f complex, a strong axial ligand to the heme is present, most probably a protonatable amino acid residue.
MeSH terms
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Amino Acid Sequence
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Cell Membrane / drug effects
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Cell Membrane / metabolism
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Cytochromes b / chemistry
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Cytochromes b / metabolism*
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Electron Spin Resonance Spectroscopy
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Electron Transport Complex III / chemistry
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Electron Transport Complex III / metabolism*
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Electrophoresis, Polyacrylamide Gel
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Gram-Positive Bacteria / cytology
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Gram-Positive Bacteria / drug effects
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Gram-Positive Bacteria / metabolism*
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Heme / chemistry
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Hydrogen-Ion Concentration
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Hydroxyquinolines / pharmacology
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Models, Molecular
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Molecular Sequence Data
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Sequence Alignment
Substances
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Hydroxyquinolines
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Rieske iron-sulfur protein
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nonyl-4-hydroxyquinoline-N-oxide
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Heme
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Cytochromes b
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Electron Transport Complex III