The cytochrome bc1 complex of Rhodobacter capsulatus: ubiquinol oxidation in a dimeric Q-cycle?

Content Provider	Semantic Scholar
Author	Gopta, Oxana A. Feniouk, Boris A. Junge, Wolfgang Mulkidjanian, Armen Y.
Copyright Year	1998
Abstract	We studied the cytochrome bc1 complex (hereafter bc) by flash excitation of Rhodobacter capsulatis chromatophores. The reduction of the high-potential heme b(h), of cytochrome b (at 561 nm) and of cytochromes c (at 552 nm) and the electrochromic absorption transients (at 524 nm) were monitored after the first and second flashes of light, respectively. We kept the ubiquinone pool oxidized in the dark and concerned for the ubiquinol formation in the photosynthetic reaction center only after the second flash. Surprisingly, the first flash caused the oxidation of about one ubiquinol per bc dimer. Based on these and other data we propose a dimeric Q-cycle where the energetically unfavorable oxidation of the first ubiquinol molecule by one of the bc monomers is driven by the energetically favorable oxidation of the second ubiquinol by the other bc monomer resulting in a pairwise oxidation of ubiquinol molecules by the dimeric bc in the dark. The residual unpaired ubiquinol supposedly remains on the enzyme and is then oxidized after the first flash.
Starting Page	18
Ending Page	22
Page Count	5
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://www.home.uni-osnabrueck.de/wjunge/public/201.pdf
Alternate Webpage(s)	http://www.macromol.uni-osnabrueck.de/paperMulk/98_Qcycle..pdf
PubMed reference number	9708922v1
Volume Number	431
Issue Number	2
Journal	FEBS letters
Language	English
Access Restriction	Open
Subject Keyword	Chromatophore Cytochrome bc1 Complex Cytochromes b Excitation Heme Photosynthetic Reaction Centers Rhodobacter capsulatus UQCRC1 gene Ubiquinone monomer oxidation sialosyl dimeric Le(x) antigen ubiquinol
Content Type	Text
Resource Type	Article