Orientation of the g-Tensor Axes of the Rieske Subunit in Cytochrome bc1 Complex
The orientation of the g-factors of the Rieske iron-sulfur protein subunit was determined in a single crystal of bovine mitochondrial cytochrome bc1 complex with stigmatellin in the Qo quinol binding site. The g-factor principal axes are skewed with respect to the Fe-Fe and S-S atom direction in the 2Fe2S cluster, which is allowed by the lack of rigorous symmetry of the cluster. The asymmetric unit in the crystal is the active dimer and the g-factor axes have slightly but noticeably different orientations relative to the iron-sulfur cluster in the two halves of the dimmer. The g {approx} 1.79 axis makes an angle of 19.8 or 40.0 with respect to the Fe-Fe direction while the g {approx} 2.024 axis is 17.6 or 35.5 from the S-S direction. These results indicate that the spectroscopic properties of the Rieske protein depend on the environment of the Rieske head domain during the catalytic cycle of cytochrome bc1 complex. This assignment of the g-factor axis directions indicates that conformations of the Rieske protein are likely the same in the cytochrome bc1 and b6f complexes and that the extent of motion of the Rieske head domain during the catalytic cycle has been highly conserved during evolution of these distantly related complexes.
- 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:
- 15007109
- Report Number(s):
- PNWD-SA-5993; 2358; TRN: US200423%%79
- Journal Information:
- Biochemistry, Vol. 43, Issue 2; Other Information: PBD: 20 Jan 2004
- Country of Publication:
- United States
- Language:
- English
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