@article{42215ec709a545f694d9c7d123437325,
title = "Excitation energy transfer kinetics of trimeric, monomeric and subunit-depleted Photosystem I from Synechocystis PCC 6803",
abstract = "Photosystem I is the most efficient photosynthetic enzyme with structure and composition highly conserved among all oxygenic phototrophs. Cyanobacterial Photosystem I is typically associated into trimers for reasons that are still debated. Almost universally, Photosystem I contains a number of long-wavelength-absorbing 'red' chlorophylls (Chls), that have a sizeable effect on the excitation energy transfer and trapping. Here we present spectroscopic comparison of trimeric Photosystem I from Synechocystis PCC 6803 with a monomeric complex from the ΔpsaL mutant and a 'minimal' monomeric complex ΔFIJL, containing only subunits A, B, C, D, E, K and M. The quantum yield of photochemistry at room temperature was the same in all complexes, demonstrating the functional robustness of this photosystem. The monomeric complexes had a reduced far-red absorption and emission equivalent to the loss of 1.5-2 red Chls emitting at 710-715 nm, whereas the longest-wavelength emission at 722 nm was not affected. The picosecond fluorescence kinetics at 77 K showed spectrally and kinetically distinct red Chls in all complexes and equilibration times of up to 50 ps. We found that the red Chls are not irreversible traps at 77 K but can still transfer excitations to the reaction centre, especially in the trimeric complexes. Structure-based F{\"o}rster energy transfer calculations support the assignment of the lowest-energy state to the Chl pair B37/B38 and the trimer-specific red Chl emission to Chls A32/B7 located at the monomer-monomer interface. These intermediate-energy red Chls facilitate energy migration from the lowest-energy states to the reaction centre.",
author = "Parveen Akhtar and Avratanu Biswas and L{\'a}szl{\'o} Kov{\'a}cs and Nathan Nelson and Lambrev, {Petar H.}",
note = "Publisher Copyright: {\textcopyright} 2021 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society",
year = "2021",
month = apr,
doi = "10.1042/BCJ20210021",
language = "אנגלית",
volume = "478",
pages = "1333--1346",
journal = "Biochemical Journal",
issn = "0264-6021",
publisher = "Portland Press Ltd.",
number = "7",
}