title: Interconversion of fast and slow forms of cytochrome bo from Escherichia coli.
abstract: The fully oxidized fast form of cytochrome bo from Escherichia coli is shown to convert spontaneously to a slow form when stored at -20 degrees C in 50 mM potassium borate, pH 8.5, containing 0.5 mM potassium EDTA. Evidence for the conversion, and that the form produced is analogous to the slow form of bovine heart cytochrome c oxidase, comes from (a) decreases in the extents of fast (k = 1-2 x 10(3) M-1 s-1) H2O2 binding and fast (k = 20-30 M-1 s-1) cyanide binding; (b) changes in the optical spectrum that are like those induced by formate, i.e., a blue shift in the Soret absorption band, loss of absorbance in the alpha and beta bands, and a red shift in the "630 nm" charge-transfer band; (c) changes in the EPR spectrum that are like those induced by formate, i.e., disappearance of signals at g = 8.6 and g = 3.71, and appearance of signals at g approximately 13, g = 3.14, and g = 2.58; and (d) appearance of a slow phase of reduction of heme o by dithionite. The mutant enzyme E286Q also converts to a slow form under the same conditions, as shown by (a) a decrease in the extent of fast H2O2 binding; (b) changes in the optical spectrum like those seen with wild-type enzyme; and (c) changes in the EPR spectrum that are like those induced by formate, i.e., disappearance of signals at g = 7.3 and g = 3.6 and appearance of signals at g approximately 13, g = 3.18, and g = 2.59.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Glynn Research Institute, Bodmin, Cornwall, U.K.
authors.forename: A J
authors.initials: AJ
authors.lastname: Moody
authors.forename: C E
authors.initials: CE
authors.lastname: Cooper
authors.forename: R B
authors.initials: RB
authors.lastname: Gennis
authors.forename: J N
authors.initials: JN
authors.lastname: Rumbley
authors.forename: P R
authors.initials: PR
authors.lastname: Rich
mesh_terms: D001881:Borates; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004227:Dithionite / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D010084:Oxidation-Reduction; D013053:Spectrophotometry; D013329:Structure-Activity Relationship; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001881:Borates; D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; D014451:Ubiquinone; D004227:Dithionite; C017168:cytochrome bo, E coli; D006861:Hydrogen Peroxide; C003741:ubiquinol