title: The cytochromes of anaerobically grown Escherichia coli. An electron-paramagnetic-resonance study of the cytochrome bd complex in situ.
abstract: The e.p.r. signals attributable to a cytochrome bd-type ubiquinol:O2 oxidoreductase (cytochrome b-558-b-595-d) were studied in a cytoplasmic membrane preparation of Escherichia coli that had been grown on glycerol with fumarate as respiratory-chain oxidant. Two major high-spin ferric haem signals were resolved on the basis of their potentiometric behaviour: a rhombic high-spin species (gx = 6.25, gy = 5.54) was assigned to haem b-595, and an axial high-spin (gx = 5.97, gy = 5.96) species was assigned to the haem d. These signals titrated with Em.7 values of 154 and 261 mV respectively, corresponding closely to optically determined values for haem b-595 and haem d. At high potentials (greater than 300 mV) the rhombic species attributable to haem b-595 underwent a partial transition to a second rhombic species with g-values of 6.24 (gx) and 5.67 (gy). The high-spin ferric haem spectra were affected by O2, CO, cyanide and pH. A low-spin ferric haem signal was observed at g = 3.3 (gz), which titrated with an Em.7 of 226 mV, and this was assigned to haem b-558. The data support a model for cytochrome bd with two ligand-binding sites, a single haem d and a single haem b-595.
authors.affiliation: Department of Biochemistry and Microbiology, University of St. Andrews, U.K.
authors.forename: R A
authors.initials: RA
authors.lastname: Rothery
authors.forename: W J
authors.initials: WJ
authors.lastname: Ingledew
mesh_terms: D002248:Carbon Monoxide / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology; D003573:Cytochrome b Group; D003580:Cytochromes; D004578:Electron Spin Resonance Spectroscopy; D045222:Electron Transport Chain Complex Proteins; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006427:Hemin; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000302:isolation & purification*; D010100:Oxygen / Q000494:pharmacology; D011199:Potentiometry
chemical_list: D003486:Cyanides; D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D006427:Hemin; D002248:Carbon Monoxide; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; D010100:Oxygen