We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Fluoride-Binding to the Escherichia coli bd-Type Ubiquinol Oxidase Studied by Visible Absorption and EPR Spectroscopies1.
- Authors
Tsubaki, Motonari; Mogi, Tatsushi; Hori, Hiroshi
- Abstract
Cytochrome bd-type ubiquinol oxidase in the aerobic respiratory chain of Escherichia coli contains two hemes b (b558 and b595) and one heme d as redox metal centers. To clarify the structure of the reaction center, we analyzed the fully oxidized enzyme by visible and EPR spectroscopies using fluoride ion as a monitoring probe. The visible spectral changes upon fluoride-binding were typical of ferric iron-chlorine species, indicating heme d as a primary binding site. The negative peak at 645 nm in the difference spectrum indicates that heme b595 also provides the low-affinity fluoride-binding site. Fluoride-binding caused a complete disappearance from the EPR spectra of the low-spin signals ascribable to heme d and spectral changes in both rhombic and axial high-spin signals. After fluoride-binding, each component of the rhombic high-spin signal showed superhyperfine splitting arising from the interaction of the unpaired spin of the heme d iron with the nuclear magnetic moment of 19F. The axial high-spin species was converted to a new rhombic high-spin species assignable to heme b595-fluoride. The g=2 component of this new species also gave 19F-superhyperfine splitting. These results indicate that both heme d and heme b595 can coordinate with a fluoride ion with different affinities in the fully oxidized state.
- Subjects
ESCHERICHIA coli; UBIQUINOL-cytochrome c reductase; PORPHYRINS; SPECTRUM analysis; ENTEROBACTERIACEAE
- Publication
Journal of Biochemistry, 1999, Vol 126, Issue 1, p98
- ISSN
0021-924X
- Publication type
Article
- DOI
10.1093/oxfordjournals.jbchem.a022442