期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 276, 期 33, 页码 30598-30607出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M102241200
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资金
- NIGMS NIH HHS [GM-20571] Funding Source: Medline
The cytochrome b(6)f complex is an obligatory electron transfer and proton-translocating enzyme in all oxygenic photosynthesis. Its operation has been described by the Q-cycle. This model proposes that electrons are transferred from plastoquinol to plastocyanin (the reductant of P700 in Photosystem I) through, obligatorily in series, the iron-sulfur and the cytochrome f redox centers in the cytochrome b6f complex. However, here we demonstrate that (a) the iron-sulfur center-dependent reductions of plastocyanin and P700 are much faster than cytochrome f reduction, both in Chlamydomonas reinhardtii cytochrome f mutants and in the wild type, and (b) the steady-state photosynthetic electron transport does not correlate with strongly inhibited cytochrome f reduction kinetics in the mutants. Thus, cytochrome f is not an obligatory intermediate for electrons flowing through the cytochrome b6f complex. The oxidation equivalents from Photosystem I are delivered to the high potential chain of the cytochrome b,f complex both at the cytochrome f level and, independently, at another site connected to the quinol-oxidizing site, possibly the iron-sulfur center.
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