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Tani K, Kanno R, Harada A, Kobayashi Y, Minamino A, Takenaka S, Nakamura N, Ji XC, Purba ER, Hall M, Yu LJ, Madigan MT, Mizoguchi A, Iwasaki K, Humbel BM, Kimura Y, Wang-Otomo ZY. High-resolution structure and biochemical properties of the LH1-RC photocomplex from the model purple sulfur bacterium, Allochromatium vinosum. Commun Biol 2024; 7:176. [PMID: 38347078 PMCID: PMC10861460 DOI: 10.1038/s42003-024-05863-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 01/26/2024] [Indexed: 02/15/2024] Open
Abstract
The mesophilic purple sulfur phototrophic bacterium Allochromatium (Alc.) vinosum (bacterial family Chromatiaceae) has been a favored model for studies of bacterial photosynthesis and sulfur metabolism, and its core light-harvesting (LH1) complex has been a focus of numerous studies of photosynthetic light reactions. However, despite intense efforts, no high-resolution structure and thorough biochemical analysis of the Alc. vinosum LH1 complex have been reported. Here we present cryo-EM structures of the Alc. vinosum LH1 complex associated with reaction center (RC) at 2.24 Å resolution. The overall structure of the Alc. vinosum LH1 resembles that of its moderately thermophilic relative Alc. tepidum in that it contains multiple pigment-binding α- and β-polypeptides. Unexpectedly, however, six Ca ions were identified in the Alc. vinosum LH1 bound to certain α1/β1- or α1/β3-polypeptides through a different Ca2+-binding motif from that seen in Alc. tepidum and other Chromatiaceae that contain Ca2+-bound LH1 complexes. Two water molecules were identified as additional Ca2+-coordinating ligands. Based on these results, we reexamined biochemical and spectroscopic properties of the Alc. vinosum LH1-RC. While modest but distinct effects of Ca2+ were detected in the absorption spectrum of the Alc. vinosum LH1 complex, a marked decrease in thermostability of its LH1-RC complex was observed upon removal of Ca2+. The presence of Ca2+ in the photocomplex of Alc. vinosum suggests that Ca2+-binding to LH1 complexes may be a common adaptation in species of Chromatiaceae for conferring spectral and thermal flexibility on this key component of their photosynthetic machinery.
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Affiliation(s)
- Kazutoshi Tani
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.
- Graduate School of Medicine, Mie University, 1577 Kurimamachiyacho, Tsu, 514-8507, Japan.
| | - Ryo Kanno
- Quantum Wave Microscopy Unit, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Ayaka Harada
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Yuki Kobayashi
- Faculty of Science, Ibaraki University, Mito, 310-8512, Japan
| | - Akane Minamino
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan
| | - Shinji Takenaka
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan
| | | | - Xuan-Cheng Ji
- Faculty of Science, Ibaraki University, Mito, 310-8512, Japan
| | - Endang R Purba
- Scientific Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Malgorzata Hall
- Scientific Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Michael T Madigan
- School of Biological Sciences, Program in Microbiology, Southern Illinois University, Carbondale, IL, 62901, USA
| | - Akira Mizoguchi
- Graduate School of Medicine, Mie University, 1577 Kurimamachiyacho, Tsu, 514-8507, Japan
| | - Kenji Iwasaki
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Bruno M Humbel
- Provost Office, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
- Department of Cell Biology and Neuroscience, Juntendo University, Graduate School of Medicine, Tokyo, 113-8421, Japan
| | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan.
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2
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Sattley WM, Swingley WD, Burchell BM, Dewey ED, Hayward MK, Renbarger TL, Shaffer KN, Stokes LM, Gurbani SA, Kujawa CM, Nuccio DA, Schladweiler J, Touchman JW, Wang-Otomo ZY, Blankenship RE, Madigan MT. Complete genome of the thermophilic purple sulfur Bacterium Thermochromatium tepidum compared to Allochromatium vinosum and other Chromatiaceae. PHOTOSYNTHESIS RESEARCH 2022; 151:125-142. [PMID: 34669148 DOI: 10.1007/s11120-021-00870-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/07/2021] [Indexed: 06/13/2023]
Abstract
The complete genome sequence of the thermophilic purple sulfur bacterium Thermochromatium tepidum strain MCT (DSM 3771T) is described and contrasted with that of its mesophilic relative Allochromatium vinosum strain D (DSM 180T) and other Chromatiaceae. The Tch. tepidum genome is a single circular chromosome of 2,958,290 base pairs with no plasmids and is substantially smaller than the genome of Alc. vinosum. The Tch. tepidum genome encodes two forms of RuBisCO and contains nifHDK and several other genes encoding a molybdenum nitrogenase but lacks a gene encoding a protein that assembles the Fe-S cluster required to form a functional nitrogenase molybdenum-iron cofactor, leaving the phototroph phenotypically Nif-. Tch. tepidum contains genes necessary for oxidizing sulfide to sulfate as photosynthetic electron donor but is genetically unequipped to either oxidize thiosulfate as an electron donor or carry out assimilative sulfate reduction, both of which are physiological hallmarks of Alc. vinosum. Also unlike Alc. vinosum, Tch. tepidum is obligately phototrophic and unable to grow chemotrophically in darkness by respiration. Several genes present in the Alc. vinosum genome that are absent from the genome of Tch. tepidum likely contribute to the major physiological differences observed between these related purple sulfur bacteria that inhabit distinct ecological niches.
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Affiliation(s)
- W Matthew Sattley
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA.
| | - Wesley D Swingley
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Brad M Burchell
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Emma D Dewey
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Mackenzie K Hayward
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Tara L Renbarger
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Kathryn N Shaffer
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Lynn M Stokes
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Sonja A Gurbani
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Catrina M Kujawa
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - D Adam Nuccio
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Jacob Schladweiler
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Jeffrey W Touchman
- School of Life Sciences, Arizona State University, Tempe, AR, 85287, USA
| | | | - Robert E Blankenship
- Departments of Chemistry and Biology, Washington University, St. Louis, MO, 63130, USA
| | - Michael T Madigan
- Department of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, IL, 62901, USA
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Kawakami T, Yu LJ, Liang T, Okazaki K, Madigan MT, Kimura Y, Wang-Otomo ZY. Crystal structure of a photosynthetic LH1-RC in complex with its electron donor HiPIP. Nat Commun 2021; 12:1104. [PMID: 33597527 PMCID: PMC7889895 DOI: 10.1038/s41467-021-21397-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 01/26/2021] [Indexed: 11/12/2022] Open
Abstract
Photosynthetic electron transfers occur through multiple components ranging from small soluble proteins to large integral membrane protein complexes. Co-crystallization of a bacterial photosynthetic electron transfer complex that employs weak hydrophobic interactions was achieved by using high-molar-ratio mixtures of a soluble donor protein (high-potential iron-sulfur protein, HiPIP) with a membrane-embedded acceptor protein (reaction center, RC) at acidic pH. The structure of the co-complex offers a snapshot of a transient bioenergetic event and revealed a molecular basis for thermodynamically unfavorable interprotein electron tunneling. HiPIP binds to the surface of the tetraheme cytochrome subunit in the light-harvesting (LH1) complex-associated RC in close proximity to the low-potential heme-1 group. The binding interface between the two proteins is primarily formed by uncharged residues and is characterized by hydrophobic features. This co-crystal structure provides a model for the detailed study of long-range trans-protein electron tunneling pathways in biological systems. The high potential iron-sulfur (HiPIP) proteins are direct electron donors to the light-harvesting-reaction center complexes (LH1-RC) in photosynthetic β- and γ-Proteobacteria. Here, the authors present the 2.9 Å crystal structure of the HiPIP-bound LH1-RC complex from the thermophilic purple sulfur bacterium Thermochromatium tepidum and discuss mechanistic implications for the electron transfer pathway.
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Affiliation(s)
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
| | - Tai Liang
- Faculty of Science, Ibaraki University, Mito, Japan
| | | | - Michael T Madigan
- Department of Microbiology, Southern Illinois University, Carbondale, IL, USA
| | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, Japan.
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Seto R, Takaichi S, Kurihara T, Kishi R, Honda M, Takenaka S, Tsukatani Y, Madigan MT, Wang-Otomo ZY, Kimura Y. Lycopene-Family Carotenoids Confer Thermostability on Photocomplexes from a New Thermophilic Purple Bacterium. Biochemistry 2020; 59:2351-2358. [DOI: 10.1021/acs.biochem.0c00192] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Ryuta Seto
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Shinichi Takaichi
- Department of Molecular Microbiology, Faculty of Life Sciences, Tokyo University of Agriculture, Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | | | - Rikako Kishi
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Mai Honda
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
| | - Shinji Takenaka
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Yusuke Tsukatani
- Institute for Extra-Cutting-Edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanagawa 237-0061, Japan
| | - Michael T. Madigan
- Department of Microbiology, Southern Illinois University, Carbondale, Illinois 62901, United States
| | | | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
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5
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Chen JH, Yu LJ, Boussac A, Wang-Otomo ZY, Kuang T, Shen JR. Properties and structure of a low-potential, penta-heme cytochrome c 552 from a thermophilic purple sulfur photosynthetic bacterium Thermochromatium tepidum. PHOTOSYNTHESIS RESEARCH 2019; 139:281-293. [PMID: 29691716 DOI: 10.1007/s11120-018-0507-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 03/30/2018] [Indexed: 06/08/2023]
Abstract
The thermophilic purple sulfur bacterium Thermochromatium tepidum possesses four main water-soluble redox proteins involved in the electron transfer behavior. Crystal structures have been reported for three of them: a high potential iron-sulfur protein, cytochrome c', and one of two low-potential cytochrome c552 (which is a flavocytochrome c) have been determined. In this study, we purified another low-potential cytochrome c552 (LPC), determined its N-terminal amino acid sequence and the whole gene sequence, characterized it with absorption and electron paramagnetic spectroscopy, and solved its high-resolution crystal structure. This novel cytochrome was found to contain five c-type hemes. The overall fold of LPC consists of two distinct domains, one is the five heme-containing domain and the other one is an Ig-like domain. This provides a representative example for the structures of multiheme cytochromes containing an odd number of hemes, although the structures of multiheme cytochromes with an even number of hemes are frequently seen in the PDB database. Comparison of the sequence and structure of LPC with other proteins in the databases revealed several characteristic features which may be important for its functioning. Based on the results obtained, we discuss the possible intracellular function of this LPC in Tch. tepidum.
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Affiliation(s)
- Jing-Hua Chen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, No. 20, Nanxincun, Xiangshan, Beijing, 100093, China
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
- University of Chinese Academy of Sciences, Yuquan Rd, Shijingshan District, Beijing, 100049, China
| | - Long-Jiang Yu
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
| | - Alain Boussac
- I2BC, SB2SM, CNRS UMR 9198, CEA Saclay, 91191, Gif-sur-Yvette, France
| | | | - Tingyun Kuang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, No. 20, Nanxincun, Xiangshan, Beijing, 100093, China
| | - Jian-Ren Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, No. 20, Nanxincun, Xiangshan, Beijing, 100093, China.
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan.
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6
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Kimura Y, Lyu S, Okoshi A, Okazaki K, Nakamura N, Ohashi A, Ohno T, Kobayashi M, Imanishi M, Takaichi S, Madigan MT, Wang-Otomo ZY. Effects of Calcium Ions on the Thermostability and Spectroscopic Properties of the LH1-RC Complex from a New Thermophilic Purple Bacterium Allochromatium tepidum. J Phys Chem B 2017; 121:5025-5032. [DOI: 10.1021/acs.jpcb.7b03341] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yukihiro Kimura
- Department
of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Shuwen Lyu
- Department
of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Akira Okoshi
- Faculty
of Science, Ibaraki University, Mito 310-8512, Japan
| | - Koudai Okazaki
- Faculty
of Science, Ibaraki University, Mito 310-8512, Japan
| | | | - Akira Ohashi
- Faculty
of Science, Ibaraki University, Mito 310-8512, Japan
| | - Takashi Ohno
- Department
of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Manami Kobayashi
- Department
of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Michie Imanishi
- Department
of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Shinichi Takaichi
- Department
of Biology, Nippon Medical School, Kyonan-cho, Musashino, Tokyo 180-0023, Japan
| | - Michael T. Madigan
- Department
of Microbiology, Southern Illinois University, Carbondale, Illinois 62901, United States
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7
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part V. {[Fe4S4](SCysγ)4} proteins. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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8
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Yu LJ, Kawakami T, Kimura Y, Wang-Otomo ZY. Structural Basis for the Unusual Q y Red-Shift and Enhanced Thermostability of the LH1 Complex from Thermochromatium tepidum. Biochemistry 2016; 55:6495-6504. [PMID: 27933779 DOI: 10.1021/acs.biochem.6b00742] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
While the majority of the core light-harvesting complexes (LH1) in purple photosynthetic bacteria exhibit a Qy absorption band in the range of 870-890 nm, LH1 from the thermophilic bacterium Thermochromatium tepidum displays the Qy band at 915 nm with an enhanced thermostability. These properties are regulated by Ca2+ ions. Substitution of the Ca2+ with other divalent metal ions results in a complex with the Qy band blue-shifted to 880-890 nm and a reduced thermostability. Following the recent publication of the structure of the Ca-bound LH1-reaction center (RC) complex [Niwa, S., et al. (2014) Nature 508, 228], we have determined the crystal structures of the Sr- and Ba-substituted LH1-RC complexes with the LH1 Qy band at 888 nm. Sixteen Sr2+ and Ba2+ ions are identified in the LH1 complexes. Both Sr2+ and Ba2+ are located at the same positions, and these are clearly different from, though close to, the Ca2+-binding sites. Conformational rearrangement induced by the substitution is limited to the metal-binding sites. Unlike the Ca-LH1-RC complex, only the α-polypeptides are involved in the Sr and Ba coordinations in LH1. The difference in the thermostability between these complexes can be attributed to the different patterns of the network formed by metal binding. The Sr- and Ba-LH1-RC complexes form a single-ring network by the LH1 α-polypeptides only, in contrast to the double-ring network composed of both α- and β-polypeptides in the Ca-LH1-RC complex. On the basis of the structural information, a combined effect of hydrogen bonding, structural integrity, and charge distribution is considered to influence the spectral properties of the core antenna complex.
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Affiliation(s)
- Long-Jiang Yu
- Faculty of Science, Ibaraki University , Mito 310-8512, Japan
| | | | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University , Nada, Kobe 657-8501, Japan
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9
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Kimura Y, Kasuga S, Unno M, Furusawa T, Osoegawa S, Sasaki Y, Ohno T, Wang-Otomo ZY. The roles of C-terminal residues on the thermal stability and local heme environment of cytochrome c' from the thermophilic purple sulfur bacterium Thermochromatium tepidum. PHOTOSYNTHESIS RESEARCH 2015; 124:19-29. [PMID: 25519852 DOI: 10.1007/s11120-014-0069-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 12/11/2014] [Indexed: 06/04/2023]
Abstract
A soluble cytochrome (Cyt) c' from thermophilic purple sulfur photosynthetic bacterium Thermochromatium (Tch.) tepidum exhibits marked thermal tolerance compared with that from the closely related mesophilic counterpart Allochromatium vinosum. Here, we focused on the difference in the C-terminal region of the two Cyts c' and examined the effects of D131 and R129 mutations on the thermal stability and local heme environment of Cyt c' by differential scanning calorimetry (DSC) and resonance Raman (RR) spectroscopy. In the oxidized forms, D131K and D131G mutants exhibited denaturing temperatures significantly lower than that of the recombinant control Cyt c'. In contrast, R129K and R129A mutants denatured at nearly identical temperatures with the control Cyt c', indicating that the C-terminal D131 is an important residue maintaining the enhanced thermal stability of Tch. tepidum Cyt c'. The control Cyt c' and all of the mutants increased their thermal stability upon the reduction. Interestingly, D131K exhibited narrow DSC curves and unusual thermodynamic parameters in both redox states. The RR spectra of the control Cyt c' exhibited characteristic bands at 1,635 and 1,625 cm(-1), ascribed to intermediate spin (IS) and high spin (HS) states, respectively. The IS/HS distribution was differently affected by the D131 and R129 mutations and pH changes. Furthermore, R129 mutants suggested the lowering of their redox potentials. These results strongly indicate that the D131 and R129 residues play significant roles in maintaining the thermal stability and modulating the local heme environment of Tch. tepidum Cyt c'.
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Affiliation(s)
- Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Nada, Kobe, 657-8501, Japan,
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10
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Hirano Y, Kimura Y, Suzuki H, Miki K, Wang ZY. Structure Analysis and Comparative Characterization of the Cytochrome c′ and Flavocytochrome c from Thermophilic Purple Photosynthetic Bacterium Thermochromatium tepidum. Biochemistry 2012; 51:6556-67. [DOI: 10.1021/bi3005522] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yu Hirano
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
- Department of Chemistry, Graduate
School of Science, Kyoto University, Sakyo-ku,
Kyoto 606-8502, Japan
| | - Yukihiro Kimura
- Organization
of Advanced Science
and Technology, Kobe University, Nada,
Kobe 657-8501, Japan
| | - Hideaki Suzuki
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
| | - Kunio Miki
- Department of Chemistry, Graduate
School of Science, Kyoto University, Sakyo-ku,
Kyoto 606-8502, Japan
| | - Zheng-Yu Wang
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
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11
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Kimura Y, Yu LJ, Hirano Y, Suzuki H, Wang ZY. Calcium ions are required for the enhanced thermal stability of the light-harvesting-reaction center core complex from thermophilic purple sulfur bacterium Thermochromatium tepidum. J Biol Chem 2008; 284:93-99. [PMID: 18977753 DOI: 10.1074/jbc.m806840200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thermochromatium tepidum is a thermophilic purple sulfur photosynthetic bacterium collected from the Mammoth Hot Springs, Yellowstone National Park. A previous study showed that the light-harvesting-reaction center core complex (LH1-RC) purified from this bacterium is highly stable at room temperature (Suzuki, H., Hirano, Y., Kimura, Y., Takaichi, S., Kobayashi, M., Miki, K., and Wang, Z.-Y. (2007) Biochim. Biophys. Acta 1767, 1057-1063). In this work, we demonstrate that thermal stability of the Tch. tepidum LH1-RC is much higher than that of its mesophilic counterparts, and the enhanced thermal stability requires Ca2+ as a cofactor. Removal of the Ca2+ from Tch. tepidum LH1-RC resulted in a complex with the same degree of thermal stability as that of the LH1-RCs purified from mesophilic bacteria. The enhanced thermal stability can be restored by addition of Ca2+ to the Ca2+-depleted LH1-RC, and this process is fully reversible. Interchange of the thermal stability between the two forms is accompanied by a shift of the LH1 Qy transition between 915 nm for the native and 880 nm for the Ca2+-depleted LH1-RC. Differential scanning calorimetry measurements reveal that degradation temperature of the native LH1-RC is 15 degrees C higher and the enthalpy change is about 28% larger than the Ca2+-depleted LH1-RC. Substitution of the Ca2+ with other metal cations caused a decrease in thermal stability of an extent depending on the properties of the cations. These results indicate that Ca2+ ions play a dual role in stabilizing the structure of the pigment-membrane protein complex and in altering its spectroscopic properties, and hence provide insight into the adaptive strategy of this photosynthetic organism to survive in extreme environments using natural resources.
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Affiliation(s)
- Yukihiro Kimura
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
| | - Long-Jiang Yu
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
| | - Yu Hirano
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
| | - Hiroaki Suzuki
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
| | - Zheng-Yu Wang
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan.
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