1
|
Marulanda Valencia W, Pandit A. Photosystem II Subunit S (PsbS): A Nano Regulator of Plant Photosynthesis. J Mol Biol 2024; 436:168407. [PMID: 38109993 DOI: 10.1016/j.jmb.2023.168407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 11/26/2023] [Accepted: 12/13/2023] [Indexed: 12/20/2023]
Abstract
Light is required for photosynthesis, but plants are often exposed to excess light, which can lead to photodamage and eventually cell death. To prevent this, they evolved photoprotective feedback mechanisms that regulate photosynthesis and trigger processes that dissipate light energy as heat, called non-photochemical quenching (NPQ). In excess light conditions, the light reaction and activity of Photosystem II (PSII) generates acidification of the thylakoid lumen, which is sensed by special pH-sensitive proteins called Photosystem II Subunit S (PsbS), actuating a photoprotective "switch" in the light-harvesting antenna. Despite its central role in regulating photosynthetic energy conversion, the molecular mechanism of PsbS as well as its interaction with partner proteins are not well understood. This review summarizes the current knowledge on the molecular structure and mechanistic aspects of the light-stress sensor PsbS and addresses open questions and challenges in the field regarding a full understanding of its functional mechanism and role in NPQ.
Collapse
Affiliation(s)
| | - Anjali Pandit
- Leiden Inst. of Chemistry, Gorlaeus Laboratory, Einsteinweg 55, 2300 RA Leiden, The Netherlands.
| |
Collapse
|
2
|
Chiariello M, Grünewald F, Zarmiento-Garcia R, Marrink SJ. pH-Dependent Conformational Switch Impacts Stability of the PsbS Dimer. J Phys Chem Lett 2023; 14:905-911. [PMID: 36662680 PMCID: PMC9900633 DOI: 10.1021/acs.jpclett.2c03760] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Accepted: 01/13/2023] [Indexed: 06/17/2023]
Abstract
The photosystem II PsbS protein triggers the photoprotective mechanism of plants by sensing the acidification of the thylakoid lumen. Despite the mechanism of action of PsbS would require a pH-dependent monomerization of the dimeric form, a clear connection between the pH-induced structural changes and the dimer stability is missing. Here, by applying constant pH coarse-grained and all-atom molecular dynamics simulations, we investigate the pH-dependent structural response of the PsbS dimer. We find that the pH variation leads to structural changes in the lumen-exposed helices, located at the dimeric interface, providing an effective switch between PsbS inactive and active form. Moreover, the monomerization free energies reveal that in the neutral pH conformation, where the network of H-bond interactions at the dimeric interface is destroyed, the protein-protein interaction is weaker. Our results show how the pH-dependent conformations of PsbS affect their dimerization propensity, which is at the basis of the photoprotective mechanism.
Collapse
Affiliation(s)
| | | | - Rubi Zarmiento-Garcia
- Groningen
Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| | - Siewert J. Marrink
- Groningen
Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 4, 9747
AG Groningen, The Netherlands
| |
Collapse
|
3
|
Krishnan-Schmieden M, Konold PE, Kennis JTM, Pandit A. The molecular pH-response mechanism of the plant light-stress sensor PsbS. Nat Commun 2021; 12:2291. [PMID: 33863895 PMCID: PMC8052336 DOI: 10.1038/s41467-021-22530-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/12/2021] [Indexed: 11/12/2022] Open
Abstract
Plants need to protect themselves from excess light, which causes photo-oxidative damage and lowers the efficiency of photosynthesis. Photosystem II subunit S (PsbS) is a pH sensor protein that plays a crucial role in plant photoprotection by detecting thylakoid lumen acidification in excess light conditions via two lumen-faced glutamates. However, how PsbS is activated under low-pH conditions is unknown. To reveal the molecular response of PsbS to low pH, here we perform an NMR, FTIR and 2DIR spectroscopic analysis of Physcomitrella patens PsbS and of the E176Q mutant in which an active glutamate has been replaced. The PsbS response mechanism at low pH involves the concerted action of repositioning of a short amphipathic helix containing E176 facing the lumen and folding of the luminal loop fragment adjacent to E71 to a 310-helix, providing clear evidence of a conformational pH switch. We propose that this concerted mechanism is a shared motif of proteins of the light-harvesting family that may control thylakoid inter-protein interactions driving photoregulatory responses.
Collapse
Affiliation(s)
| | - Patrick E Konold
- Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, Amsterdam, The Netherlands
| | - John T M Kennis
- Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
| | - Anjali Pandit
- Dept. of Solid-State NMR, Leiden Inst. of Chemistry, Leiden University, Leiden, The Netherlands.
| |
Collapse
|
4
|
Fine tuning of the photosystem II major antenna mobility within the thylakoid membrane of higher plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183059. [PMID: 31518553 DOI: 10.1016/j.bbamem.2019.183059] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 08/16/2019] [Accepted: 09/04/2019] [Indexed: 12/15/2022]
Abstract
Depending on the amount of light, the photosystem II (PSII) antennae or Light Harvesting Complexes (LHCII) switch between two states within the thylakoid membranes of higher plants, i.e., a light-harvesting and a photoprotective mode. This switch is co-regulated by a pH gradient (ΔpH) across the membrane and the interaction with the PSII subunit S (PsbS) that is proposed to induce LHCII aggregation. Herein we employ all-atom and coarse-grained molecular simulations of the major LHCII trimer at low and excess ΔpH, as well as in complexation with PsbS within a native thylakoid membrane model. Our results demonstrate the aggregation potential of LHCII and, consistent with the experimental literature, reveal the role of PsbS at atomic resolution. PsbS alters the LHCII-thylakoid lipid interactions and restores the LHCII mobility that is lost in the transition to photoprotective conditions (low lumenal pH). In agreement with this finding, diffusion of the integral membrane protein LHCII is dependent on both, electrostatic interactions and hydrophobic mismatch, while it does not obey the Saffman-Delbrück diffusion model.
Collapse
|
5
|
Cell-free soluble expression of the membrane protein PsbS. Protein Expr Purif 2019; 159:17-20. [DOI: 10.1016/j.pep.2019.02.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 02/13/2019] [Accepted: 02/13/2019] [Indexed: 11/20/2022]
|
6
|
Liguori N, Campos SRR, Baptista A, Croce R. Molecular Anatomy of Plant Photoprotective Switches: The Sensitivity of PsbS to the Environment, Residue by Residue. J Phys Chem Lett 2019; 10:1737-1742. [PMID: 30908067 PMCID: PMC6477805 DOI: 10.1021/acs.jpclett.9b00437] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 03/25/2019] [Indexed: 05/15/2023]
Abstract
Under strong sunlight, plants avoid photooxidation by quenching the excess absorbed energy. Quenching is triggered by PsbS, a membrane protein that is activated and deactivated by the light-dependent pH changes in the thylakoid lumen. The mechanism of action of this protein is unknown, but it was suggested that several glutamates act as pH sensors. However, the p Ka of glutamate is several pH units below the physiological values in the lumen. Thus, how can PsbS sense the pH of the lumen, and how does it respond to it? By applying a nonstandard molecular dynamics method that treats pH explicitly, we show that the lumen-exposed glutamates of PsbS have strongly shifted p Ka values and that such shifts are crucial for the pH sensitivity in physiological conditions. We also demonstrate that protonation drives a systematic unfolding of a region key for protein-protein interactions, indicating that PsbS response to pH is a functional conformational switch.
Collapse
Affiliation(s)
- Nicoletta Liguori
- Department
of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Sara R. R. Campos
- Instituto
de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
| | - António
M. Baptista
- Instituto
de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
| | - Roberta Croce
- Department
of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| |
Collapse
|
7
|
Wei Y, Wang Y, Wu X, Shu S, Sun J, Guo S. Redox and thylakoid membrane proteomic analysis reveals the Momordica (Momordica charantia L.) rootstock-induced photoprotection of cucumber leaves under short-term heat stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 136:98-108. [PMID: 30660678 DOI: 10.1016/j.plaphy.2019.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 01/08/2019] [Accepted: 01/09/2019] [Indexed: 06/09/2023]
Abstract
Heat stress adversely affects plant physiological and metabolic processes and is considered an important constraint on crop growth and productivity in agriculture worldwide. Grafting techniques are capable of mitigating various stresses. Here, compared with self-grafted cucumbers subjected to 42 °C heat stress for 24 h, we found that Momordica-grafted cucumbers exhibited higher cytomembrane thermostability, less photoinhibition reflected by their chlorophyll fluorescence, and a reduction in oxidative stress. To better understand the mechanism, optimized Blue-Native/SDS-PAGE two-dimensional electrophoresis (2-DE) was firstly applied to entire thylakoid membrane of grafted cucumbers, and 25 significantly differential accumulated protein spots were identified by MALDI-TOF/TOF MS analysis. The proteomic analysis revealed that high temperatures suppressed the accumulation of 13 proteins in self-grafted cucumbers, while Momordica rootstock stimulated the accumulation of 12 of these proteins. The transcriptional analysis indicated that grafting onto Momordica significantly increased the expression of genes that encode the photosystem II subunit S (PsbS) and minor light-harvesting complexes (CP24, CP26 and CP29.1), which are closely associated with non-photochemical quenching (NPQ) after heat shock. Immunoblotting for PsbS corroborated the Momordica-induced acceleration of heat dissipation. Taken together, Momordica rootstock alleviated heat-induced photoinhibition by maintaining intracellular redox homeostasis, stabilizing the protein library of the thylakoid membrane and modulating NPQ in the scions.
Collapse
Affiliation(s)
- Ying Wei
- Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yu Wang
- Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xinyi Wu
- Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Sheng Shu
- Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China; Suqian Academy of Protected Horticulture, Nanjing Agricultural University, Suqian, 223800, China
| | - Jin Sun
- Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China; Suqian Academy of Protected Horticulture, Nanjing Agricultural University, Suqian, 223800, China
| | - Shirong Guo
- Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China; Suqian Academy of Protected Horticulture, Nanjing Agricultural University, Suqian, 223800, China.
| |
Collapse
|
8
|
Daskalakis V. Protein-protein interactions within photosystem II under photoprotection: the synergy between CP29 minor antenna, subunit S (PsbS) and zeaxanthin at all-atom resolution. Phys Chem Chem Phys 2018; 20:11843-11855. [PMID: 29658553 DOI: 10.1039/c8cp01226a] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The assembly and disassembly of protein complexes within cells are crucial life-sustaining processes. In photosystem II (PSII) of higher plants, there is a delicate yet obscure balance between light harvesting and photo-protection under fluctuating light conditions, that involves protein-protein complexes. Recent breakthroughs in molecular dynamics (MD) simulations are combined with new approaches herein to provide structural and energetic insight into such a complex between the CP29 minor antenna and the PSII subunit S (PsbS). The microscopic model involves extensive sampling of bound and dissociated states at atomic resolution in the presence of photo-protective zeaxanthin (Zea), and reveals well defined protein-protein cross-sections. The complex is placed within PSII, and macroscopic connections are emerging (PsbS-CP29-CP24-CP47) along the energy transfer pathways from the antenna to the PSII core. These connections explain macroscopic observations in the literature, while the previously obscured atomic scale details are now revealed. The implications of these findings are discussed in the context of the Non-Photochemical Quenching (NPQ) of chlorophyll fluorescence, the down-regulatory mechanism of photosynthesis, that enables the protection of PSII against excess excitation load. Zea is found at the PsbS-CP29 cross-section and a pH-dependent equilibrium between PsbS dimer/monomers and the PsbS-CP29 dissociation/association is identified as the target for engineering tolerant plants with increased crop and biomass yields. Finally, the new MD based approaches can be used to probe protein-protein interactions in general, and the PSII structure provided can initiate large scale molecular simulations of the photosynthetic apparatus, under NPQ conditions.
Collapse
Affiliation(s)
- Vangelis Daskalakis
- Department of Environmental Science and Technology, Cyprus University of Technology (CUT), 30 Archbishop Kyprianou Str., 3603, Limassol, Cyprus.
| |
Collapse
|