The Interaction of the Rieske Iron-Sulfur Protein with Occupants of the Q(o)-site of the bc(1) Complex, Probed by Electron Spin Echo Envelope Modulation

Journal Article · Thu Feb 15 04:00:00 EST 2001 · Journal of Biological Chemistry

OSTI ID:15005606

Samoilova, Rimma I ^[1]; Kolling, D ^[2]; Uzawa, T ^[2]; Iwasaki, T ^[2]; Crofts, Antony R ^[3]; Dikanov, S A ^[2]

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1. 9042
2. Russian Academy of Sciences
3. 3600

The bifurcated reaction at the Q(o)-site of the bc(1) complex provides the mechanistic basis of the proton pumping activity through which the complex conserves redox energy in the proton gradient. Structural information about the binding of quinone at the site is lacking, because the site is vacant in crystals of the native complexes. We now report the first structural characterization of the interaction of the native quinone occupant with the Rieske iron-sulfur protein in the bc(1) complex of Rhodobacter sphaeroides, using high resolution EPR. We have compared the binding configuration in the presence of quinone with the known structures for the complex with stigmatellin and myxothiazol. We have shown by using EPR and orientation-selective electron spin echo envelope modulation (ESEEM) measurements of the iron-sulfur protein that when quinone is present in the site, the isotropic hyperfine constant of one of the N(delta) atoms of a liganding histidine of the[2Fe-2S] cluster is similar to that observed when stigmatellin is present and different from the configuration in the presence of myxothiazol. The spectra also show complementary differences in nitrogen quadrupole splittings in some orientations. We suggest that the EPR characteristics, the ESEEM spectra, and the hyperfine couplings reflect a similar interaction between the iron-sulfur protein and the quinone or stigmatellin and that the N(delta) involved is that of a histidine (equivalent to His-161 in the chicken mitochondrial complex) that forms both a ligand to the cluster and a hydrogen bond with a carbonyl oxygen atom of the Q(o)-site occupant

• Research Organization: Pacific Northwest National Lab., Richland, WA (US), Environmental Molecular Sciences Lab. (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 15005606
• Journal Information: Journal of Biological Chemistry, Journal Name: Journal of Biological Chemistry Journal Issue: 7 Vol. 277
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
ATOMS
BENZOQUINONES
CARBONYLS
CONFIGURATION
ENVIRONMENTAL MOLECULAR SCIENCES LABORATORY
NULL
HISTIDINE
HYDROGEN
MODULATION
NITROGEN
OCCUPANTS
OXYGEN
PROTEINS
PROTONS
QUADRUPOLES
SPECTRA