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Wilson S, Clarke CD, Carbajal MA, Buccafusca R, Fleck RA, Daskalakis V, Ruban AV. Hydrophobic Mismatch in the Thylakoid Membrane Regulates Photosynthetic Light Harvesting. J Am Chem Soc 2024. [PMID: 38759103 DOI: 10.1021/jacs.4c05220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2024]
Abstract
The ability to harvest light effectively in a changing environment is necessary to ensure efficient photosynthesis and crop growth. One mechanism, known as qE, protects photosystem II (PSII) and regulates electron transfer through the harmless dissipation of excess absorbed photons as heat. This process involves reversible clustering of the major light-harvesting complexes of PSII (LHCII) in the thylakoid membrane and relies upon the ΔpH gradient and the allosteric modulator protein PsbS. To date, the exact role of PsbS in the qE mechanism has remained elusive. Here, we show that PsbS induces hydrophobic mismatch in the thylakoid membrane through dynamic rearrangement of lipids around LHCII leading to observed membrane thinning. We found that upon illumination, the thylakoid membrane reversibly shrinks from around 4.3 to 3.2 nm, without PsbS, this response is eliminated. Furthermore, we show that the lipid digalactosyldiacylglycerol (DGDG) is repelled from the LHCII-PsbS complex due to an increase in both the pKa of lumenal residues and in the dipole moment of LHCII, which allows for further conformational change and clustering in the membrane. Our results suggest a mechanistic role for PsbS as a facilitator of a hydrophobic mismatch-mediated phase transition between LHCII-PsbS and its environment. This could act as the driving force to sort LHCII into photoprotective nanodomains in the thylakoid membrane. This work shows an example of the key role of the hydrophobic mismatch process in regulating membrane protein function in plants.
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Affiliation(s)
- Sam Wilson
- Department of Biochemistry, School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Charlea D Clarke
- Department of Biochemistry, School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - M Alejandra Carbajal
- Centre for Ultrastructural Imaging, King's College London, London SE1 1UL, United Kingdom
| | - Roberto Buccafusca
- Department of Chemistry, School of Physical and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Roland A Fleck
- Centre for Ultrastructural Imaging, King's College London, London SE1 1UL, United Kingdom
| | - Vangelis Daskalakis
- Department of Chemical Engineering, School of Engineering, University of Patras, Patras 26504, Greece
| | - Alexander V Ruban
- Department of Biochemistry, School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
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Krishnarjuna B, Ramamoorthy A. Detergent-Free Isolation of Membrane Proteins and Strategies to Study Them in a Near-Native Membrane Environment. Biomolecules 2022; 12:1076. [PMID: 36008970 PMCID: PMC9406181 DOI: 10.3390/biom12081076] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 07/31/2022] [Accepted: 08/02/2022] [Indexed: 02/06/2023] Open
Abstract
Atomic-resolution structural studies of membrane-associated proteins and peptides in a membrane environment are important to fully understand their biological function and the roles played by them in the pathology of many diseases. However, the complexity of the cell membrane has severely limited the application of commonly used biophysical and biochemical techniques. Recent advancements in NMR spectroscopy and cryoEM approaches and the development of novel membrane mimetics have overcome some of the major challenges in this area. For example, the development of a variety of lipid-nanodiscs has enabled stable reconstitution and structural and functional studies of membrane proteins. In particular, the ability of synthetic amphipathic polymers to isolate membrane proteins directly from the cell membrane, along with the associated membrane components such as lipids, without the use of a detergent, has opened new avenues to study the structure and function of membrane proteins using a variety of biophysical and biological approaches. This review article is focused on covering the various polymers and approaches developed and their applications for the functional reconstitution and structural investigation of membrane proteins. The unique advantages and limitations of the use of synthetic polymers are also discussed.
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Affiliation(s)
- Bankala Krishnarjuna
- Department of Chemistry and Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry and Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
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Patel JH, Pollock NL, Maher J, Rothnie AJ, Allen M. The function of BK channels extracted and purified within SMALPs. Biochem J. [PMID: 35851603 PMCID: PMC9444072 DOI: 10.1042/bcj20210628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 06/27/2022] [Accepted: 07/19/2022] [Indexed: 11/17/2022]
Abstract
Human BK channels are large voltage and Ca2+-activated K+ channels, involved in several important functions within the body. The core channel is a tetramer of α subunits, and its function is modulated by the presence of β and γ accessory subunits. BK channels composed of α subunits, as well as BK channels composed of α and β1 subunits, were successfully solubilised from HEK cells with styrene maleic acid (SMA) polymer and purified by nickel affinity chromatography. Native SMA–PAGE analysis of the purified proteins showed the α subunits were extracted as a tetramer. In the presence of β1 subunits, they were co-extracted with the α subunits as a heteromeric complex. Purified SMA lipid particles (SMALPs) containing BK channel could be inserted into planar lipid bilayers (PLB) and single channel currents recorded, showing a high conductance (≈260 pS), as expected. The open probability was increased in the presence of co-purified β1 subunits. However, voltage-dependent gating of the channel was restricted. In conclusion, we have demonstrated that SMA can be used to effectively extract and purify large, complex, human ion channels, from low expressing sources. That these large channels can be incorporated into PLB from SMALPs and display voltage-dependent channel activity. However, the SMA appears to reduce the voltage dependent gating of the channels.
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Hawkins OP, Jahromi CPT, Gulamhussein AA, Nestorow S, Bahra T, Shelton C, Owusu-Mensah QK, Mohiddin N, O'Rourke H, Ajmal M, Byrnes K, Khan M, Nahar NN, Lim A, Harris C, Healy H, Hasan SW, Ahmed A, Evans L, Vaitsopoulou A, Akram A, Williams C, Binding J, Thandi RK, Joby A, Guest A, Tariq MZ, Rasool F, Cavanagh L, Kang S, Asparuhov B, Jestin A, Dafforn TR, Simms J, Bill RM, Goddard AD, Rothnie AJ. Membrane protein extraction and purification using partially-esterified SMA polymers. Biochim Biophys Acta Biomembr 2021; 1863:183758. [PMID: 34480878 PMCID: PMC8484863 DOI: 10.1016/j.bbamem.2021.183758] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/16/2021] [Accepted: 08/24/2021] [Indexed: 12/15/2022]
Abstract
Styrene maleic acid (SMA) polymers have proven to be very successful for the extraction of membrane proteins, forming SMA lipid particles (SMALPs), which maintain a lipid bilayer around the membrane protein. SMALP-encapsulated membrane proteins can be used for functional and structural studies. The SMALP approach allows retention of important protein-annular lipid interactions, exerts lateral pressure, and offers greater stability than traditional detergent solubilisation. However, SMA polymer does have some limitations, including a sensitivity to divalent cations and low pH, an absorbance spectrum that overlaps with many proteins, and possible restrictions on protein conformational change. Various modified polymers have been developed to try to overcome these challenges, but no clear solution has been found. A series of partially-esterified variants of SMA (SMA 2625, SMA 1440 and SMA 17352) has previously been shown to be highly effective for solubilisation of plant and cyanobacterial thylakoid membranes. It was hypothesised that the partial esterification of maleic acid groups would increase tolerance to divalent cations. Therefore, these partially-esterified polymers were tested for the solubilisation of lipids and membrane proteins, and their tolerance to magnesium ions. It was found that all partially esterified polymers were capable of solubilising and purifying a range of membrane proteins, but the yield of protein was lower with SMA 1440, and the degree of purity was lower for both SMA 1440 and SMA 17352. SMA 2625 performed comparably to SMA 2000. SMA 1440 also showed an increased sensitivity to divalent cations. Thus, it appears the interactions between SMA and divalent cations are more complex than proposed and require further investigation.
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Affiliation(s)
- Olivia P Hawkins
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | | | - Aiman A Gulamhussein
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Stephanie Nestorow
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Taranpreet Bahra
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Christian Shelton
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Quincy K Owusu-Mensah
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Naadiya Mohiddin
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Hannah O'Rourke
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mariam Ajmal
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Kara Byrnes
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Madiha Khan
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Nila N Nahar
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Arcella Lim
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Cassandra Harris
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Hannah Healy
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Syeda W Hasan
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Asma Ahmed
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Lora Evans
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Afroditi Vaitsopoulou
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Aneel Akram
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Chris Williams
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Johanna Binding
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Rumandeep K Thandi
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Aswathy Joby
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Ashley Guest
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mohammad Z Tariq
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Farah Rasool
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Luke Cavanagh
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Simran Kang
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Biser Asparuhov
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Aleksandr Jestin
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Timothy R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - John Simms
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Roslyn M Bill
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alan D Goddard
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alice J Rothnie
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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Brady NG, Workman CE, Cawthon B, Bruce BD, Long BK. Protein Extraction Efficiency and Selectivity of Esterified Styrene-Maleic Acid Copolymers in Thylakoid Membranes. Biomacromolecules 2021; 22:2544-2553. [PMID: 34038122 DOI: 10.1021/acs.biomac.1c00274] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amphiphilic styrene-maleic acid copolymers (SMAs) have been shown to effectively extract membrane proteins surrounded by an annulus of native membrane lipids via the formation of nanodiscs. Recent reports have shown that 2-butoxyethanol-functionalized SMA derivatives promote the extraction of membrane proteins from thylakoid membranes, whereas unfunctionalized SMA is essentially ineffective. However, it is unknown how the extent of functionalization and identity of sidechains impact protein solubilization and specificity. Herein, we show that the monoesterification of an SMA polymer with hydrophobic alkoxy ethoxylate sidechains leads to an increased solubilization efficiency (SE) of trimeric photosystem I (PSI) from the membranes of cyanobacterium Thermosynechococcus elongatus. The specific SMA polymer used in this study, PRO 10235, cannot encapsulate single PSI trimers from this cyanobacterium; however, as it is functionalized with alkoxy ethoxylates of increasing alkoxy chain length, a clear increase in the trimeric PSI SE is observed. Furthermore, an exponential increase in the SE is observed when >50% of the maleic acid repeat units are monoesterified with long alkoxy ethoxylates, suggesting that the PSI extraction mechanism is highly dependent on both the number and length of the attached side chains.
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Affiliation(s)
- Nathan G Brady
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville 37996-1939, Tennessee, United States
| | - Cameron E Workman
- Department of Chemistry, University of Tennessee, Knoxville 37996-1600, Tennessee, United States
| | - Bridgie Cawthon
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville 37996-0840, Tennessee, United States
| | - Barry D Bruce
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville 37996-1939, Tennessee, United States.,Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville 37996-0840, Tennessee, United States
| | - Brian K Long
- Department of Chemistry, University of Tennessee, Knoxville 37996-1600, Tennessee, United States
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