Distinct structural modulation of photosystem I and lipid environment stabilizes its tetrameric assembly

Chen, Ming; Perez-Boerema, Annemarie; Zhang, Laixing; Li, Yanxue; Yang, Maojun; Li, Shizhong; Amunts, Alexey

doi:10.1038/s41477-020-0610-x

Cited by 34 publications

(64 citation statements)

References 51 publications

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“…The red loop we added to the Synechocystis WT PSI based on T. elongatus structure can also be found in Thermosynechococcus vulcanus 46 , Fischerella thermalis 47 and Nostoc sp. PCC 7120 48 . The short loop present in Synechocystis can be found in Synechococcus sp.…”

Section: Discussionmentioning

confidence: 99%

The structure of a red-shifted photosystem I reveals a red site in the core antenna

et al. 2020

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Photosystem I coordinates more than 90 chlorophylls in its core antenna while achieving near perfect quantum efficiency. Low energy chlorophylls (also known as red chlorophylls) residing in the antenna are important for energy transfer dynamics and yield, however, their precise location remained elusive. Here, we construct a chimeric Photosystem I complex in Synechocystis PCC 6803 that shows enhanced absorption in the red spectral region. We combine Cryo-EM and spectroscopy to determine the structure−function relationship in this red-shifted Photosystem I complex. Determining the structure of this complex reveals the precise architecture of the low energy site as well as large scale structural heterogeneity which is probably universal to all trimeric Photosystem I complexes. Identifying the structural elements that constitute red sites can expand the absorption spectrum of oxygenic photosynthetic and potentially modulate light harvesting efficiency.

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Section: Discussionmentioning

confidence: 99%

The structure of a red-shifted photosystem I reveals a red site in the core antenna

et al. 2020

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“…A notable exception to the surprising invariance in PsaL after monomerization is the absence of its short C-terminal α-helix. This short α-helix, which is oriented roughly parallel to the membrane plane on the lumenal side, is believed to make crucial contacts with neighboring PSI monomers in the process of trimerization 8,16 or in the formation of tetrameric PSI [22][23][24] . This short α-helix is also absent in our monomer X-ray crystal structure and the same short α-helix has been reported to lose its secondary structure in the His-tagged C-terminus of the PSI monomer from Synechocystis sp.…”

Section: Discussionmentioning

confidence: 99%

“…PCC 6803 solved at 4.0 Å resolution by X-ray crystallography 14 , all structures of cyanobacterial PSI have been determined from trimeric complexes 8,[15][16][17][18][19][20][21] or the recently discovered tetrameric PSI from Anabaena sp. PCC 7120 [22][23][24] and Chroococcidiopsis sp. TS-821 25 .…”

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confidence: 99%

Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster

et al. 2021

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A high-resolution structure of trimeric cyanobacterial Photosystem I (PSI) from Thermosynechococcus elongatus was reported as the first atomic model of PSI almost 20 years ago. However, the monomeric PSI structure has not yet been reported despite long-standing interest in its structure and extensive spectroscopic characterization of the loss of red chlorophylls upon monomerization. Here, we describe the structure of monomeric PSI from Thermosynechococcus elongatus BP-1. Comparison with the trimer structure gave detailed insights into monomerization-induced changes in both the central trimerization domain and the peripheral regions of the complex. Monomerization-induced loss of red chlorophylls is assigned to a cluster of chlorophylls adjacent to PsaX. Based on our findings, we propose a role of PsaX in the stabilization of red chlorophylls and that lipids of the surrounding membrane present a major source of thermal energy for uphill excitation energy transfer from red chlorophylls to P700.

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“…The structure of the PSI core from cyanobacteria has been analyzed at atomic resolutions by X‐ray crystallography and cryo‐electron micorscopy (cryo‐EM) (Jordan et al, 2001; Malavath et al, 2018; Kato et al, 2019; Zheng et al, 2019; Chen et al, 2020), which revealed the detailed arrangement of protein subunits and cofactors within the PSI core. The crystal structure of PSI‐LHCI supercomplex from higher plants was also analyzed at 2.6–2.8 Å resolutions (Mazor et al, 2015, 2017; Qin et al, 2015; Pan et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…While this approach gives an increased resolution, the low isomorphism between different crystals may yield an electron density map that is difficult to interpret in some regions (Rupp, 2010), especially with respect to the lipid molecules, as the electron density of lipids is rather weak. However, lipids is known to play important roles in the assembly of large membrane protein complexes (Zheng et al, 2019; Chen et al, 2020), and therefore it is important to determine the positions of lipids accurately. In order to investigate the detailed structure of the plant PSI‐LHCI supercomplex, we optimized the conditions of crystallization and cryoprotection to improve the resolution.…”

Section: Introductionmentioning

confidence: 99%

Structure of plant photosystem I−light harvesting complex I supercomplex at 2.4 Å resolution

Wang

et al. 2021

JIPB

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Photosystem I (PSI) is one of the two photosystems in photosynthesis, and performs a series of electron transfer reactions leading to the reduction of ferredoxin. In higher plants, PSI is surrounded by four light‐harvesting complex I (LHCI) subunits, which harvest and transfer energy efficiently to the PSI core. The crystal structure of PSI‐LHCI supercomplex has been analyzed up to 2.6 Å resolution, providing much information on the arrangement of proteins and cofactors in this complicated supercomplex. Here we have optimized crystallization conditions, and analyzed the crystal structure of PSI‐LHCI at 2.4 Å resolution. Our structure showed some shift of the LHCI, especially the Lhca4 subunit, away from the PSI core, suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core. We identified five new lipids in the structure, most of them are located in the gap region between the Lhca subunits and the PSI core. These lipid molecules may play important roles in binding of the Lhca subunits to the core, as well as in the assembly of the supercomplex. The present results thus provide novel information for the elucidation of the mechanisms for the light‐energy harvesting, transfer and assembly of this supercomplex.

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Distinct structural modulation of photosystem I and lipid environment stabilizes its tetrameric assembly

Cited by 34 publications

References 51 publications

The structure of a red-shifted photosystem I reveals a red site in the core antenna

The structure of a red-shifted photosystem I reveals a red site in the core antenna

Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster

Structure of plant photosystem I−light harvesting complex I supercomplex at 2.4 Å resolution

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