Molecular Probes of Quinol Oxidation by the Cytochrome b6f complex
EMSL Project ID
2358
Abstract
Cytochrome (cyt) b6f complex, a plastocyanin-quinol oxidoreductase, serves a central role in photosynthetic electron transport. The complex catalyzes the oxidation and reduction of quinone species at two sites on the complex: quinol oxidase (Qo) site and quinol reductase (Qi) site. The mechanism of catalysis at the Qo site is being intensely-debated, with groups supporting either one (single occupancy) or two (double occupancy) quinone species binding to the site and participating in the reaction. Several chemical inhibitors, which have been successfully used to probe these sites and deciphering the kinetic mechanism of the enzyme. We have recently produced evidence that two molecules of the quinone analog, dibromomethylisopropylbenzoquinone (DBMIB), bind simultaneously to the Qo site. DBMIB represents an excellent system in which to test and study double occupancy models. We proposed to use continuous-wave (CW) and pulsed X-band EPR techniques, to probe the nature of 'inhibitor double occupancy' in this system. The ultimate goal is to understand 1) how one and two DBMIB molecules interact with the complex; and 2) how they are oriented within the Qo binding pocket. The facilities at EMSL, including especially the expertise of Dr. M. Bowman, are ideally suited for this work. This would require approximately 280 hours of time on the X-band EPR spectrometer that is available at EMSL.
Project Details
Project type
Capability Research
Start Date
2002-01-01
End Date
2005-01-06
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bowman MK, EA Berry, AG Roberts, and DM Kramer. 2004. "Orientation of the g-Tensor Axes of the Rieske Subunit in Cytochrome bc1 Complex." Biochemistry 43(2):430-436.
Cape JL, JR Strahan, MJ Lenaeus, BA Yuknis, TT Le, J Shepherd, MK Bowman, and DM Kramer. 2005. "THE RESPIRATORY SUBSTRATE RHODOQUINOL INDUCES Q-CYCLE BYPASS REACTIONS IN THE YEAST CYTOCHROME bc1 COMPLEX - MECHANISTIC AND PHYSIOLOGICAL IMPLICATIONS." Journal of Biological Chemistry 280(41):34654-34660.
Cooley JW, AG Roberts, MK Bowman, DM Kramer, and F Daldal. 2004. "The Raised Midpoint Potential of the [2Fe2S] Cluster of Cytochrome bc1 is Mediated by Both the Q(o) Site Occupants and the Head Domain Position of the Fe-S Protein Subunit ." Biochemistry 43(8):2217-2227.
Muller FL, AG Roberts, MK Bowman, and DM Kramer. 2003. "The Architecture of the Qo Site of Cytochrome bc1 Complex Probed by Superoxide Production." Biochemistry 42(21):6493-6499.
Roberts AG, MK Bowman, and DM Kramer. 2002. "Certain Metal Ions are Inhibitors of Cytochrome b (6) f Complex 'Rieske' Iron-Sulfur Protein Domain Movements." Biochemistry 41(12):4070-4079.