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Huang X, Vasilev C, Swainsbury D, Hunter C. Excitation energy transfer in proteoliposomes reconstituted with LH2 and RC-LH1 complexes from Rhodobacter sphaeroides. Biosci Rep 2024; 44:BSR20231302. [PMID: 38227291 PMCID: PMC10876425 DOI: 10.1042/bsr20231302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 12/30/2023] [Accepted: 01/16/2024] [Indexed: 01/17/2024] Open
Abstract
Light-harvesting 2 (LH2) and reaction-centre light-harvesting 1 (RC-LH1) complexes purified from the photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were reconstituted into proteoliposomes either separately, or together at three different LH2:RC-LH1 ratios, for excitation energy transfer studies. Atomic force microscopy (AFM) was used to investigate the distribution and association of the complexes within the proteoliposome membranes. Absorption and fluorescence emission spectra were similar for LH2 complexes in detergent and liposomes, indicating that reconstitution retains the structural and optical properties of the LH2 complexes. Analysis of fluorescence emission shows that when LH2 forms an extensive series of contacts with other such complexes, fluorescence is quenched by 52.6 ± 1.4%. In mixed proteoliposomes, specific excitation of carotenoids in LH2 donor complexes resulted in emission of fluorescence from acceptor RC-LH1 complexes engineered to assemble with no carotenoids. Extents of energy transfer were measured by fluorescence lifetime microscopy; the 0.72 ± 0.08 ns lifetime in LH2-only membranes decreases to 0.43 ± 0.04 ns with a ratio of 2:1 LH2 to RC-LH1, and to 0.35 ± 0.05 ns for a 1:1 ratio, corresponding to energy transfer efficiencies of 40 ± 14% and 51 ± 18%, respectively. No further improvement is seen with a 0.5:1 LH2 to RC-LH1 ratio. Thus, LH2 and RC-LH1 complexes perform their light harvesting and energy transfer roles when reconstituted into proteoliposomes, providing a way to integrate native, non-native, engineered and de novo designed light-harvesting complexes into functional photosynthetic systems.
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Affiliation(s)
- Xia Huang
- Department of Biological Sciences, Xi’an Jiaotong-Liverpool University, Suzhou, Jiangsu 215123, China
- Jinan Guoke Medical Technology Development Co., Ltd, Jinan, Shandong 250101, China
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - Cvetelin Vasilev
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - David J.K. Swainsbury
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
- School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, U.K
| | - C. Neil Hunter
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
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2
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Šímová I, Kuznetsova V, Gardiner AT, Šebelík V, Koblížek M, Fuciman M, Polívka T. Carotenoid responds to excess energy dissipation in the LH2 complex from Rhodoblastus acidophilus. Photosynth Res 2022; 154:75-87. [PMID: 36066816 DOI: 10.1007/s11120-022-00952-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
The functions of both (bacterio) chlorophylls and carotenoids in light-harvesting complexes have been extensively studied during the past decade, yet, the involvement of BChl a high-energy Soret band in the cascade of light-harvesting processes still remains a relatively unexplored topic. Here, we present transient absorption data recorded after excitation of the Soret band in the LH2 complex from Rhodoblastus acidophilus. Comparison of obtained data to those recorded after excitation of rhodopin glucoside and B800 BChl a suggests that no Soret-to-Car energy transfer pathway is active in LH2 complex. Furthermore, a spectrally rich pattern observed in the spectral region of rhodopin glucoside ground state bleaching (420-550 nm) has been assigned to an electrochromic shift. The results of global fitting analysis demonstrate two more features. A 6 ps component obtained exclusively after excitation of the Soret band has been assigned to the response of rhodopin glucoside to excess energy dissipation in LH2. Another time component, ~ 450 ps, appearing independently of the excitation wavelength was assigned to BChl a-to-Car triplet-triplet transfer. Presented data demonstrate several new features of LH2 complex and its behavior following the excitation of the Soret band.
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Affiliation(s)
- Ivana Šímová
- Department of Physics, Faculty of Science, University of South Bohemia, Branišovská, 1760, 370 05, Ceske Budejovice, Czech Republic
| | - Valentyna Kuznetsova
- Department of Physics, Faculty of Science, University of South Bohemia, Branišovská, 1760, 370 05, Ceske Budejovice, Czech Republic
| | - Alastair T Gardiner
- Laboratory of Anoxygenic Phototrophs, Institute of Microbiology, Czech Academy of Sciences, 379 81, Třeboň, Czech Republic
| | - Václav Šebelík
- Department of Physics, Faculty of Science, University of South Bohemia, Branišovská, 1760, 370 05, Ceske Budejovice, Czech Republic
- Dynamical Spectroscopy, Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, 85748, Garching b. Munich, Germany
| | - Michal Koblížek
- Laboratory of Anoxygenic Phototrophs, Institute of Microbiology, Czech Academy of Sciences, 379 81, Třeboň, Czech Republic
| | - Marcel Fuciman
- Department of Physics, Faculty of Science, University of South Bohemia, Branišovská, 1760, 370 05, Ceske Budejovice, Czech Republic
| | - Tomáš Polívka
- Department of Physics, Faculty of Science, University of South Bohemia, Branišovská, 1760, 370 05, Ceske Budejovice, Czech Republic.
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3
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Du Y, Khan M, Fang N, Ma F, Du H, Tan Z, Wang H, Yin S, Wei X. Berberine Attenuates Cell Motility via Inhibiting Inflammation-Mediated Lysyl Hydroxylase-2 and Glycolysis. Front Pharmacol 2022; 13:856777. [PMID: 35559258 PMCID: PMC9086160 DOI: 10.3389/fphar.2022.856777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 03/22/2022] [Indexed: 11/13/2022] Open
Abstract
Lysyl hydroxylase-2 (LH2) involves in the hydroxylation of telopeptide lysine residues during collagen deposition. Recent studies indicate that interleukin (IL)-6 generated by the chronic inflammation disease may trigger the LH2 expression to accelerate cell motility. Berberine is the alkaloid derived from the traditional Chinese medicine Coptis chinensis, which displays potential anti-inflammatory activity in multiple diseases. The anti-inflammatory activity of berberine has been confirmed by reducing proinflammatory cytokines such as IL-6, IL-8, and IFN-γ. However, whether and how berberine inhibits cellular motility against metastatic spread in triple-negative breast cancer (TNBC) has not been demonstrated, and the underlying mechanism remains unclear. We investigated the effects of berberine on the inflammatory cytokine secretion, cell proliferation, and migration in vitro and further explored the effect of berberine on growth and metastasis in vivo. Berberine restrained TNBC cell proliferation, motility, and glycolysis process in a dose-dependent way. The secretion of IL-6 was abrogated by berberine in TNBC cells, and IL-6-stimulated cell migration was inhibited by berberine. Mechanistically, berberine remarkably suppressed LH2 expression at both mRNA and protein levels. LH2 depletion led to decreasing the antimotility effect of berberine, and this phenomenon was related to the suppressed glycolysis after LH2 inhibition. Conversely, ectopic restoration of LH2 could further increase the antimotility effect of berberine. Moreover, berberine was confirmed to inhibit cell growth and motility in vivo, and the expression of LH2 and glycolytic enzymes was also blocked by berberine in vivo. Collectively, this study indicated that berberine could be a promising therapeutic drug via regulating LH2 for TNBC.
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Affiliation(s)
- Yishan Du
- Department of Geriatrics, Affiliated Provincial Hospital of Anhui Medical University, Anhui Medical University, Hefei, China
| | - Muhammad Khan
- Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Nana Fang
- Department of Pathophysiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Fang Ma
- Center for Scientific Research of Anhui Medical University, Hefei, China
| | - Hongzhi Du
- School of Pharmacy, Hubei University of Chinese Medicine, Wuhan, China
| | - Zhenya Tan
- Department of Pathophysiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Hua Wang
- Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Shi Yin
- Department of Geriatrics, Affiliated Provincial Hospital of Anhui Medical University, Anhui Medical University, Hefei, China.,Anhui Provincial Key Laboratory of Tumor Immunotherapy and Nutrition Therapy, Hefei, China
| | - Xiaohui Wei
- Department of Pathophysiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
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Swainsbury DJK, Faries KM, Niedzwiedzki DM, Martin EC, Flinders AJ, Canniffe DP, Shen G, Bryant DA, Kirmaier C, Holten D, Hunter CN. Engineering of B800 bacteriochlorophyll binding site specificity in the Rhodobacter sphaeroides LH2 antenna. Biochim Biophys Acta Bioenerg 2019; 1860:209-23. [PMID: 30414933 DOI: 10.1016/j.bbabio.2018.11.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 10/19/2018] [Accepted: 11/07/2018] [Indexed: 11/22/2022]
Abstract
The light-harvesting 2 complex (LH2) of the purple phototrophic bacterium Rhodobacter sphaeroides is a highly efficient, light-harvesting antenna that allows growth under a wide-range of light intensities. In order to expand the spectral range of this antenna complex, we first used a series of competition assays to measure the capacity of the non-native pigments 3-acetyl chlorophyll (Chl) a, Chl d, Chl f or bacteriochlorophyll (BChl) b to replace native BChl a in the B800 binding site of LH2. We then adjusted the B800 site and systematically assessed the binding of non-native pigments. We find that Arg-10 of the LH2 β polypeptide plays a crucial role in binding specificity, by providing a hydrogen-bond to the 3-acetyl group of native and non-native pigments. Reconstituted LH2 complexes harbouring the series of (B)Chls were examined by transient absorption and steady-state fluorescence spectroscopies. Although slowed 10-fold to ~6 ps, energy transfer from Chl a to B850 BChl a remained highly efficient. We measured faster energy-transfer time constants for Chl d (3.5 ps) and Chl f (2.7 ps), which have red-shifted absorption maxima compared to Chl a. BChl b, red-shifted from the native BChl a, gave extremely rapid (≤0.1 ps) transfer. These results show that modified LH2 complexes, combined with engineered (B)Chl biosynthesis pathways in vivo, have potential for retaining high efficiency whilst acquiring increased spectral range.
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5
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Southall J, Henry SL, Gardiner AT, Roszak AW, Mullen W, Carey AM, Kelly SM, de Percin Northumberland CO, Cogdell RJ. Characterisation of a pucBA deletion mutant from Rhodopseudomonas palustris lacking all but the pucBA d genes. Photosynth Res 2018; 135:9-21. [PMID: 28567613 PMCID: PMC5783997 DOI: 10.1007/s11120-017-0386-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 04/08/2017] [Indexed: 06/01/2023]
Abstract
Rhodopseudomonas palustris is a species of purple photosynthetic bacteria that has a multigene family of puc genes that encode the alpha and beta apoproteins, which form the LH2 complexes. A genetic dissection strategy has been adopted in order to try and understand which spectroscopic form of LH2 these different genes produce. This paper presents a characterisation of one of the deletion mutants generated in this program, the pucBAd only mutant. This mutant produces an unusual spectroscopic form of LH2 that only has a single large NIR absorption band at 800 nm. Spectroscopic and pigment analyses on this complex suggest that it has basically a similar overall structure as that of the wild-type HL LH2 complex. The mutant has the unique phenotype where the mutant LH2 complex is only produced when cells are grown at LL. At HL the mutant only produces the LH1-RC core complex.
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Affiliation(s)
- June Southall
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK.
| | - Sarah L Henry
- Biomedical Engineering, School of Engineering, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - Alastair T Gardiner
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - Aleksander W Roszak
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - William Mullen
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - Anne-Marie Carey
- Center for Innovations in Medicine, The Biodesign Institute, Arizona State University, 1001 S. McAllister Ave., Tempe, AZ, 85287-5001, USA
| | - Sharon M Kelly
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | | | - Richard J Cogdell
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
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6
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Thyrhaug E, Lincoln CN, Branchi F, Cerullo G, Perlík V, Šanda F, Lokstein H, Hauer J. Carotenoid-to-bacteriochlorophyll energy transfer through vibronic coupling in LH2 from Phaeosprillum molischianum. Photosynth Res 2018; 135:45-54. [PMID: 28523607 PMCID: PMC5783993 DOI: 10.1007/s11120-017-0398-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 05/09/2017] [Indexed: 06/07/2023]
Abstract
The peripheral light-harvesting antenna complex (LH2) of purple photosynthetic bacteria is an ideal testing ground for models of structure-function relationships due to its well-determined molecular structure and ultrafast energy deactivation. It has been the target for numerous studies in both theory and ultrafast spectroscopy; nevertheless, certain aspects of the convoluted relaxation network of LH2 lack a satisfactory explanation by conventional theories. For example, the initial carotenoid-to-bacteriochlorophyll energy transfer step necessary on visible light excitation was long considered to follow the Förster mechanism, even though transfer times as short as 40 femtoseconds (fs) have been observed. Such transfer times are hard to accommodate by Förster theory, as the moderate coupling strengths found in LH2 suggest much slower transfer within this framework. In this study, we investigate LH2 from Phaeospirillum (Ph.) molischianum in two types of transient absorption experiments-with narrowband pump and white-light probe resulting in 100 fs time resolution, and with degenerate broadband 10 fs pump and probe pulses. With regard to the split Qx band in this system, we show that vibronically mediated transfer explains both the ultrafast carotenoid-to-B850 transfer, and the almost complete lack of transfer to B800. These results are beyond Förster theory, which predicts an almost equal partition between the two channels.
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Affiliation(s)
- Erling Thyrhaug
- Photonics Institute, TU Wien, Gußhausstraße 27, 1040, Vienna, Austria
| | - Craig N Lincoln
- Photonics Institute, TU Wien, Gußhausstraße 27, 1040, Vienna, Austria
| | - Federico Branchi
- Dipartimento di Fisica, IFN-CNR, Politecnico di Milano, Piazza L. da Vinci, 32, 20133, Milan, Italy
| | - Giulio Cerullo
- Dipartimento di Fisica, IFN-CNR, Politecnico di Milano, Piazza L. da Vinci, 32, 20133, Milan, Italy
| | - Václav Perlík
- Faculty of Mathematics and Physics, Institute of Physics, Charles University, Ke Karlovu 5, 12116, Prague, Czech Republic
| | - František Šanda
- Faculty of Mathematics and Physics, Institute of Physics, Charles University, Ke Karlovu 5, 12116, Prague, Czech Republic
| | - Heiko Lokstein
- Department of Chemical Physics and Optics, Charles University, Ke Karlovu 3, 12116, Praha 2, Czech Republic
| | - Jürgen Hauer
- Photonics Institute, TU Wien, Gußhausstraße 27, 1040, Vienna, Austria.
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7
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Razjivin AP, Lukashev EP, Kompanets VO, Kozlovsky VS, Ashikhmin AA, Chekalin SV, Moskalenko AA, Paschenko VZ. Excitation energy transfer from the bacteriochlorophyll Soret band to carotenoids in the LH2 light-harvesting complex from Ectothiorhodospira haloalkaliphila is negligible. Photosynth Res 2017; 133:289-295. [PMID: 28205063 DOI: 10.1007/s11120-017-0341-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 01/18/2017] [Indexed: 06/06/2023]
Abstract
Pathways of intramolecular conversion and intermolecular electronic excitation energy transfer (EET) in the photosynthetic apparatus of purple bacteria remain subject to debate. Here we experimentally tested the possibility of EET from the bacteriochlorophyll (BChl) Soret band to the singlet S2 level of carotenoids using femtosecond pump-probe measurements and steady-state fluorescence excitation and absorption measurements in the near-ultraviolet and visible spectral ranges. The efficiency of EET from the Soret band of BChl to S2 of the carotenoids in light-harvesting complex LH2 from the purple bacterium Ectothiorhodospira haloalkaliphila appeared not to exceed a few percent.
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Affiliation(s)
- A P Razjivin
- Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia, 119991.
| | - E P Lukashev
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia, 119991
| | - V O Kompanets
- Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow, Russia, 142190
| | - V S Kozlovsky
- Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia, 119991
| | - A A Ashikhmin
- Institute of Fundamental Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow Region, Russia, 142290
| | - S V Chekalin
- Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow, Russia, 142190
| | - A A Moskalenko
- Institute of Fundamental Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow Region, Russia, 142290
| | - V Z Paschenko
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia, 119991
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8
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Malý P, Gruber JM, Cogdell RJ, Mančal T, van Grondelle R. Ultrafast energy relaxation in single light-harvesting complexes. Proc Natl Acad Sci U S A 2016; 113:2934-9. [PMID: 26903650 DOI: 10.1073/pnas.1522265113] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub-100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump-probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations.
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Niedzwiedzki DM, Dilbeck PL, Tang Q, Mothersole DJ, Martin EC, Bocian DF, Holten D, Hunter CN. Functional characteristics of spirilloxanthin and keto-bearing Analogues in light-harvesting LH2 complexes from Rhodobacter sphaeroides with a genetically modified carotenoid synthesis pathway. Biochim Biophys Acta 2015; 1847:640-55. [PMID: 25871644 DOI: 10.1016/j.bbabio.2015.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 04/01/2015] [Accepted: 04/03/2015] [Indexed: 11/24/2022]
Abstract
Light-harvesting 2 (LH2) complexes from a genetically modified strain of the purple photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. Carotenoid synthesis in the Rba. sphaeroides strain was engineered to redirect carotenoid production away from spheroidene into the spirilloxanthin synthesis pathway. The strain assembles LH2 antennas with substantial amounts of spirilloxanthin (total double-bond conjugation length N=13) if grown anaerobically and of keto-bearing long-chain analogs [2-ketoanhydrorhodovibrin (N=13), 2-ketospirilloxanthin (N=14) and 2,2'-diketospirilloxanthin (N=15)] if grown semi-aerobically (with ratios that depend on growth conditions). We present the photophysical, electronic, and vibrational properties of these carotenoids, both isolated in organic media and assembled within LH2 complexes. Measurements of excited-state energy transfer to the array of excitonically coupled bacteriochlorophyll a molecules (B850) show that the mean lifetime of the first singlet excited state (S1) of the long-chain (N≥13) carotenoids does not change appreciably between organic media and the protein environment. In each case, the S1 state appears to lie lower in energy than that of B850. The energy-transfer yield is ~0.4 in LH2 (from the strain grown aerobically or semi-aerobically), which is less than half that achieved for LH2 that contains short-chain (N≤11) analogues. Collectively, the results suggest that the S1 excited state of the long-chain (N≥13) carotenoids participates little if at all in carotenoid-to-BChl a energy transfer, which occurs predominantly via the carotenoid S2 excited state in these antennas.
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Affiliation(s)
- Dariusz M Niedzwiedzki
- Photosynthetic Antenna Research Center, Washington University, St. Louis, MO 63130, USA.
| | - Preston L Dilbeck
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
| | - Qun Tang
- Department of Chemistry, University of California Riverside, Riverside, CA 92521, USA
| | - David J Mothersole
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Elizabeth C Martin
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - David F Bocian
- Department of Chemistry, University of California Riverside, Riverside, CA 92521, USA
| | - Dewey Holten
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
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10
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Yue H, Zhao C, Li K, Yang S. Absorption spectral change of peripheral-light harvesting complexes 2 induced by magnesium protoporphyrin IX monomethyl ester association. Spectrochim Acta A Mol Biomol Spectrosc 2015; 137:1153-1157. [PMID: 25305606 DOI: 10.1016/j.saa.2014.08.132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 08/15/2014] [Accepted: 08/31/2014] [Indexed: 06/04/2023]
Abstract
Several spectrally different types of peripheral light harvesting complexes (LH) have been reported in anoxygenic phototrophic bacteria in response to environmental changes. In this study, two spectral forms of LH2 (T-LH2 and U-LH2) were isolated from Rhodobacter azotoformans. The absorption of T-LH2 was extremely similar to the LH2 isolated from Rhodobacter sphaeroides. U-LH2 showed an extra peak at ∼423 nm in the carotenoid region. To explore the spectral origin of this absorption peak, the difference in pigment compositions of two LH2 was analyzed. Spheroidene and bacteriochlorophyll aP were both contained in the two LH2. And magnesium protoporphyrin IX monomethyl ester (MPE) was only contained in U-LH2. It is known that spheroidene and bacteriochlorophyll aP do not produce ∼423 nm absorption peak either in vivo or in vitro. Whether MPE accumulation was mainly responsible for the formation of the ∼423 nm peak? The interactions between MPE and different proteins were further studied. The results showed that the maximum absorption of MPE was red-shifted from ∼415 nm to ∼423 nm when it was mixed with T-LH2 and its apoproteins, nevertheless, the Qy transitions of the bound bacteriochlorophylls in LH2 were almost unaffected, which indicated that the formation of the ∼423 nm peak was related to MPE-LH2 protein interaction. MPE did not bind to sites involved in the spectral tuning of BChls, but the conformation of integral LH2 was affected by MPE association, the alkaline stability of U-LH2 was lower than T-LH2, and the fluorescence intensity at 860 nm was decreased after MPE combination.
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Affiliation(s)
- Huiying Yue
- Department of Bioengineering and Biotechnology, Huaqiao University, Xiamen 361021, China.
| | - Chungui Zhao
- Department of Bioengineering and Biotechnology, Huaqiao University, Xiamen 361021, China.
| | - Kai Li
- Department of Bioengineering and Biotechnology, Huaqiao University, Xiamen 361021, China.
| | - Suping Yang
- Department of Bioengineering and Biotechnology, Huaqiao University, Xiamen 361021, China.
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11
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Cranston LJ, Roszak AW, Cogdell RJ. Crystallization and preliminary X-ray diffraction analysis of the peripheral light-harvesting complex LH2 from Marichromatium purpuratum. Acta Crystallogr F Struct Biol Commun 2014; 70:808-13. [PMID: 24915099 DOI: 10.1107/s2053230x14009303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 04/24/2014] [Indexed: 11/11/2022]
Abstract
LH2 from the purple photosynthetic bacterium Marichromatium (formerly known as Chromatium) purpuratum is an integral membrane pigment-protein complex that is involved in harvesting light energy and transferring it to the LH1-RC `core' complex. The purified LH2 complex was crystallized using the sitting-drop vapour-diffusion method at 294 K. The crystals diffracted to a resolution of 6 Å using synchrotron radiation and belonged to the tetragonal space group I4, with unit-cell parameters a=b=109.36, c=80.45 Å. The data appeared to be twinned, producing apparent diffraction symmetry I422. The tetragonal symmetry of the unit cell and diffraction for the crystals of the LH2 complex from this species reveal that this complex is an octamer.
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Affiliation(s)
- Laura J Cranston
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow Biomedical Research Centre, 120 University Place, Glasgow G12 8TA, Scotland
| | - Aleksander W Roszak
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow Biomedical Research Centre, 120 University Place, Glasgow G12 8TA, Scotland
| | - Richard J Cogdell
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow Biomedical Research Centre, 120 University Place, Glasgow G12 8TA, Scotland
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