9GC2

Cryo-EM structure of Arabidopsis thaliana PSI-LHCI- a603-NH mutant

9GC2 の概要

• エントリーDOI: 10.2210/pdb9gc2/pdb
• 関連するPDBエントリー: 9GBI
• EMDBエントリー: 51227
• 分子名称: Chlorophyll a-b binding protein 6, chloroplastic, Photosystem I reaction center subunit III, chloroplastic, Photosystem I reaction center subunit V, chloroplastic, ... (28 entities in total)
• 機能のキーワード: psi-lhci, arabidopsis thaliana, light harvesting, far-red absorption, photosynthesis
• 由来する生物種: Arabidopsis thaliana (thale cress); 詳細
• タンパク質・核酸の鎖数: 17
• 化学式量合計: 547881.36

構造登録者

Capaldi, S.,Chaves-Sanjuan, A.,Bonnet, D.M.V.,Bassi, R. (登録日: 2024-08-01, 公開日: 2025-08-13, 最終更新日: 2025-11-19)

主引用文献

Capaldi, S.,Guardini, Z.,Montepietra, D.,Pagliuca, V.F.,Amelii, A.,Betti, E.,John, C.,Pedraza-Gonzalez, L.,Cupellini, L.,Mennucci, B.,Bonnet, D.M.V.,Chaves-Sanjuan, A.,Dall'Osto, L.,Bassi, R.
Structural determinants for red-shifted absorption in higher-plants Photosystem I.
New Phytol., 248:2331-2346, 2025

PubMed Abstract: Higher plants Photosystem I absorbs far-red light, enriched under vegetation canopies, through long-wavelength Chls to enhance photon capture. Far-red absorption originates from Chl pairs within the Lhca3 and Lhca4 subunits of the LHCI antenna, known as the 'red cluster', including Chls a603 and a609. We used reverse genetics to produce an Arabidopsis mutant devoid of red-shifted absorption, and we obtained high-resolution cryogenic electron microscopy structures of PSI-LHCI complexes from both wild-type and mutant plants. Computed excitonic coupling values suggested contributions from additional nearby pigment molecules, namely Chl a615 and violaxanthin in the L2 site, to far-red absorption. We investigated the structural determinants of far-red absorption by producing further Arabidopsis transgenic lines and analyzed the spectroscopic effects of mutations targeting these chromophores. The two structures solved were used for quantum mechanics calculations, revealing that excitonic interactions alone cannot explain far-red absorption, while charge transfer states were needed for accurate spectral simulations. Our findings demonstrate that the molecular mechanisms of light-harvesting under shaded conditions rely on very precise tuning of chromophore interactions, whose understanding is crucial for designing light-harvesting complexes with engineered absorption spectra.

PubMed: 40955088
DOI: 10.1111/nph.70562

実験手法

ELECTRON MICROSCOPY (3.29 Å)