engleski

Sifting the elements of FNR-TROL bifurcation

The last step of photosynthetic light-to-chemical energy conversion is the electron transfer from reduced ferredoxin (Fd) to NADP+. This reaction is catalysed by the flavoenzyme FNR (ferredoxin:NADP+ oxidoreductase), which utilizes two reduced Fds to produce one molecule of NADPH. In order to prevent Fd from promiscuous electron partitioning, the electron transfer reaction Fd>FNR>NADPH has to proceed rapidly and preferentially at the vicinity of photosystem I. FNR dimer is tethered to vascular plant photosynthetic membranes via an integral membrane protein TROL (thylakoid rhodanase-like protein). Soluble protein Tic62 also participates in FNR sequestration and activity control. FNR-TROL interaction prioritizes linear electron transfer (LET). When FNR complex is released from the TROL, highly efficient electron sink is activated. This pathway is faster than methyl viologen-mediated ROS propagation and represents so far undescribed mechanism of photosynthesis regulation. Apart from thylakoid membranes, TROL is targeted to the inner chloroplast envelope. Apparently, regulation involving stromal processing peptidase is crucial for this sorting. Finally, FNR-TROL bifurcation is embedded into redox responses of the entire plant and may even represent the source element linking

photosynthesis ; ROS ; anthocyanins ; protein import and sorting ; EPR ; PAM

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