| 15178478 |
Joliot P, Beal D, Joliot A: Cyclic electron flow under saturating excitation of dark-adapted Arabidopsis leaves. Biochim Biophys Acta. 2004 Jun 7;1656(2-3):166-76.
The rate of cyclic electron flow measured in dark-adapted leaves under aerobic conditions submitted to a saturating illumination has been performed by the analysis of the transmembrane potential changes induced by a light to dark transfer. Using a new highly sensitive spectrophotometric technique, a rate of the cyclic flow of approximately 130 s (-1) has been measured in the presence or absence of 3-(3,4-dichloro-phenyl)-1,1-dimethylurea (DCMU). This value is approximately 1.5 times larger than that previously reported [Proc. Natl. Acad. Sci. U. S. A. 99 (2001) 10209]. We have characterized in the presence or absence of DCMU charge recombination process (t (1/2) approximately 60 micros) that involves P (700)(+) and very likely the reduced form of the iron sulfur acceptor F (X). This led to conclude that, under saturating illumination, the PSI centers involved in the cyclic pathway have most of the iron sulfur acceptors F (A) and F (B) reduced. In the proposed mechanism, electrons are transferred from a ferredoxin bound to a site localized on the stromal side of the cytochrome b (6) f complex to the Q (i) site. Two possible models of the organization of the membrane complexes are discussed, in which the cyclic and linear electron transfer chains are isolated one from the other. |
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