engleski

The roles of ferredoxin:NADP(+) oxidoreductase in photosynthetic energy conversion

Plant photosynthetic linear electron transport chain (LET) transfers electrons generated by photosystems II and I to a small iron-sulphur protein ferredoxin (Fd). Fd acts simultaneously as a bottleneck and as a branching point that distributes high-energy electrons to several alternative electron transport chains and a multitude of enzymes. However, the dominant pathway in chloroplasts is the one that produces NADPH, by the activity of ferredoxin-NADP+-oxidoreductase (FNR). FNR is a soluble protein that exists in several isoforms and utilizes two reduced Fds to produce one molecule of NADPH. We have demonstrated that thylakoid rhodanase-like protein TROL acts as a bona fide photosynthetic membrane attachment point for FNR1, although other associations with thylakoid and inner envelope membranes have been described. We have also proposed a scheme for the dynamic FNR recruitment to TROL2, 3. We speculate that TROL-FNR interaction represents branching point between electron-conserving and electron-dissipating pathways. Alternative Fd-dependent pathways downstream of PSI and different from the LET may become dominant by the dynamic detachment of FNR form TROL, thus suggesting a novel mechanism of photosynthesis regulation. Also, efficient scavenging of O2.- radicals by FNR-dependent mechanism can be envisaged.

FNR; PSI; TROL; Arabidopsis

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