The monomeric photosystem I-light-harvesting antenna complex I (PSI-LHCI) supercomplex from the extremophilic red alga represents an intermediate evolutionary link between the cyanobacterial PSI reaction center and its green algal/higher plant counterpart. We show that the PSI-LHCI supercomplex is characterized by robustness in various extreme conditions. By a combination of biochemical, spectroscopic, mass spectrometry, and electron microscopy/single particle analyses, we dissected three molecular mechanisms underlying the inherent robustness of the PSI-LHCI supercomplex: (1) the accumulation of photoprotective zeaxanthin in the LHCI antenna and the PSI reaction center; (2) structural remodeling of the LHCI antenna and adjustment of the effective absorption cross section; and (3) dynamic readjustment of the stoichiometry of the two PSI-LHCI isomers and changes in the oligomeric state of the PSI-LHCI supercomplex, accompanied by dissociation of the PsaK core subunit. We show that the largest low light-treated PSI-LHCI supercomplex can bind up to eight Lhcr antenna subunits, which are organized as two rows on the PsaF/PsaJ side of the core complex. Under our experimental conditions, we found no evidence of functional coupling of the phycobilisomes with the PSI-LHCI supercomplex purified from various light conditions, suggesting that the putative association of this antenna with the PSI supercomplex is absent or may be lost during the purification procedure.
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http://dx.doi.org/10.1104/pp.17.01022 | DOI Listing |
Nat Struct Mol Biol
January 2025
Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
The nicotinamide adenine dinucleotide phosphate (NADPH) dehydrogenase (NDH) complex is crucial for photosynthetic cyclic electron flow and respiration, transferring electrons from ferredoxin to plastoquinone while transporting H across the chloroplast membrane. This process boosts adenosine triphosphate production, regardless of NADPH levels. In flowering plants, NDH forms a supercomplex with photosystem I, enhancing its stability under high light.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
December 2024
Marine Biotechnology Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China.
Biochim Biophys Acta Bioenerg
January 2025
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China; University of Chinese Academy of Sciences, 100049 Beijing, China; China National Botanical Garden, 100093 Beijing, China; Academician Workstation of Agricultural High-Tech Industrial Area of the Yellow River Delta, National Center of Technology Innovation for Comprehensive Utilization of Saline-Alkali Land, Dongying 257300, China. Electronic address:
Photosystem I (PSI) is a large membrane photosynthetic complex that harvests sunlight and drives photosynthetic electron transport. In both green algae and higher plants, PSI's ultrafast energy transfer and charge separation kinetics have been characterized. In contrast, it is not yet clear in Physcomitrella patens, even though moss is one of the earliest land plants and represents a critical stage in plant evolution.
View Article and Find Full Text PDFElife
October 2024
Faculty of Agriculture, Shizuoka University, Shizuoka, Japan.
New Phytol
December 2024
National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki, 444-8585, Japan.
We explored the adaptive mechanisms of Ostreococcus tauri, a marine picophytoplankton with a ubiquitous ocean presence. We aimed to understand its photosynthetic acclimation, as featured in the cryo-EM structure of its photosystem I (PSI) supercomplex. This structure revealed a unique composition involving a phosphorylated Lhcp trimer bound to the PSI core along with two additional Lhcp trimers, suggesting potential state transitions for photoacclimation.
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