The detection and characterization by electron-paramagnetic-resonance spectroscopy of iron-sulphur proteins and other electron-transport components in chromatophores from the purple bacterium Chromatium.
Low-temperature e.p.r. (electron-paramagnetic-resonance) spectroscopy was used to detect electron-transport components in Chromatium chromatophores with e.p.r. signals in the g=2.00 region. High-potential iron protein (E(m8.0)=+325mV, where E(m8.0) is the midpoint potential at pH8) and a second component (g=1.90, E(m8.0)=+285mV) are oxidized in illuminated chromatophores. Two iron-sulphur proteins (g=1.94) with E(m8.0)=-290mV and E(m8.0)=-50mV are present. One (E(m8.0)=-50mV) is reduced on illumination. A component (g=1.82) with E(m8.0)=-135mV is photoreduced at 10 degrees K. The midpoint potential of this component is altered by o-phenanthroline and pH. The properties of this component suggest that it is the primary electron acceptor of a photochemical system. Another component (g=1.98) also has some of the properties of a primary electron acceptor, but its function cannot be completely defined. These results show that iron-sulphur proteins are present in the electron-transport system of Chromatium and indicate their role in electron transport.
D020130:Bacterial Chromatophores / Q000032:analysis*; D001426:Bacterial Proteins / Q000032:analysis* / Q000378:metabolism; D002844:Chromatium / Q000032:analysis* / Q000166:cytology / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D007501:Iron; D008667:Metalloproteins / Q000032:analysis* / Q000378:metabolism; D010084:Oxidation-Reduction; D010618:Phenanthrolines; D010785:Photophosphorylation; D011199:Potentiometry; D013455:Sulfur; D013696:Temperature
D001426:Bacterial Proteins; D008667:Metalloproteins; D010618:Phenanthrolines; D013455:Sulfur; D007501:Iron