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Tani K, Kanno R, Ji XC, Hall M, Yu LJ, Kimura Y, Madigan MT, Mizoguchi A, Humbel BM, Wang-Otomo ZY. Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum. Biochemistry 2021; 60:2483-2491. [PMID: 34323477 DOI: 10.1021/acs.biochem.1c00360] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rhodospirillum (Rsp.) rubrum is one of the most widely used model organisms in bacterial photosynthesis. This purple phototroph is characterized by the presence of both rhodoquinone (RQ) and ubiquinone as electron carriers and bacteriochlorophyll (BChl) a esterified at the propionic acid side chain by geranylgeraniol (BChl aG) instead of phytol. Despite intensive efforts, the structure of the light-harvesting-reaction center (LH1-RC) core complex from Rsp. rubrum remains at low resolutions. Using cryo-EM, here we present a robust new view of the Rsp. rubrum LH1-RC at 2.76 Å resolution. The LH1 complex forms a closed, slightly elliptical ring structure with 16 αβ-polypeptides surrounding the RC. Our biochemical analysis detected RQ molecules in the purified LH1-RC, and the cryo-EM density map specifically positions RQ at the QA site in the RC. The geranylgeraniol side chains of BChl aG coordinated by LH1 β-polypeptides exhibit a highly homologous tail-up conformation that allows for interactions with the bacteriochlorin rings of nearby LH1 α-associated BChls aG. The structure also revealed key protein-protein interactions in both N- and C-terminal regions of the LH1 αβ-polypeptides, mainly within a face-to-face structural subunit. Our high-resolution Rsp. rubrum LH1-RC structure provides new insight for evaluating past experimental and computational results obtained with this old organism over many decades and lays the foundation for more detailed exploration of light-energy conversion, quinone transport, and structure-function relationships in this pigment-protein complex.
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Affiliation(s)
- Kazutoshi Tani
- Graduate School of Medicine, Mie University, Tsu, Mie 514-8507, Japan
| | - Ryo Kanno
- 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
| | - Xuan-Cheng Ji
- Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan
| | - Malgorzata Hall
- 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
| | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, Hyogo 657-8501, Japan
| | - Michael T Madigan
- School of Biological Sciences, Southern Illinois University, Carbondale, Illinois 62901, United States
| | - Akira Mizoguchi
- Graduate School of Medicine, Mie University, Tsu, Mie 514-8507, Japan
| | - Bruno M Humbel
- 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
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Kimura Y, Yamashita T, Seto R, Imanishi M, Honda M, Nakagawa S, Saga Y, Takenaka S, Yu LJ, Madigan MT, Wang-Otomo ZY. Circular dichroism and resonance Raman spectroscopies of bacteriochlorophyll b-containing LH1-RC complexes. PHOTOSYNTHESIS RESEARCH 2021; 148:77-86. [PMID: 33834357 DOI: 10.1007/s11120-021-00831-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 03/19/2021] [Indexed: 06/12/2023]
Abstract
The core light-harvesting complexes (LH1) in bacteriochlorophyll (BChl) b-containing purple phototrophic bacteria are characterized by a near-infrared absorption maximum around 1010 nm. The determinative cause for this ultra-redshift remains unclear. Here, we present results of circular dichroism (CD) and resonance Raman measurements on the purified LH1 complexes in a reaction center-associated form from a mesophilic and a thermophilic Blastochloris species. Both the LH1 complexes displayed purely positive CD signals for their Qy transitions, in contrast to those of BChl a-containing LH1 complexes. This may reflect differences in the conjugation system of the bacteriochlorin between BChl b and BChl a and/or the differences in the pigment organization between the BChl b- and BChl a-containing LH1 complexes. Resonance Raman spectroscopy revealed remarkably large redshifts of the Raman bands for the BChl b C3-acetyl group, indicating unusually strong hydrogen bonds formed with LH1 polypeptides, results that were verified by a published structure. A linear correlation was found between the redshift of the Raman band for the BChl C3-acetyl group and the change in LH1-Qy transition for all native BChl a- and BChl b-containing LH1 complexes examined. The strong hydrogen bonding and π-π interactions between BChl b and nearby aromatic residues in the LH1 polypeptides, along with the CD results, provide crucial insights into the spectral and structural origins for the ultra-redshift of the long-wavelength absorption maximum of BChl b-containing phototrophs.
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Affiliation(s)
- Y Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan.
| | - T Yamashita
- Faculty of Science, Ibaraki University, Mito, 310-8512, Japan
| | - R Seto
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan
| | - M Imanishi
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan
| | - M Honda
- Faculty of Science, Ibaraki University, Mito, 310-8512, Japan
| | - S Nakagawa
- Department of Chemistry, Kindai University, Higashi-Osaka, 577-8502, Japan
| | - Y Saga
- Department of Chemistry, Kindai University, Higashi-Osaka, 577-8502, Japan
| | - S Takenaka
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, 657-8501, Japan
| | - L-J Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - M T Madigan
- Department of Microbiology, Southern Illinois University, Carbondale, IL, 62901, USA
| | - Z-Y Wang-Otomo
- Faculty of Science, Ibaraki University, Mito, 310-8512, Japan.
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Tuning the Photophysical Features of Self-Assembling Photoactive Polypeptides for Light-Harvesting. MATERIALS 2019; 12:ma12213554. [PMID: 31671513 PMCID: PMC6862114 DOI: 10.3390/ma12213554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 10/25/2019] [Accepted: 10/27/2019] [Indexed: 01/03/2023]
Abstract
The LH1 complex is the major light-harvesting antenna of purple photosynthetic bacteria. Its role is to capture photons, and then store them and transfer the excitation energy to the photosynthetic reaction center. The structure of LH1 is modular and it cooperatively self-assembles from the subunits composed of short transmembrane polypeptides that reversibly bind the photoactive cofactors: bacteriochlorophyll and carotenoid. LH1 assembly, the intra-complex interactions and the light-harvesting features of LH1 can be controlled in micellar media by varying the surfactant concentration and by adding carotenoid and/or a co-solvent. By exploiting this approach, we can manipulate the size of the assembly, the intensity of light absorption, and the energy and lifetime of its first excited singlet state. For instance, via the introduction of Ni-substituted bacteriochlorophyll into LH1, the lifetime of this electronic state of the antenna can be shortened by almost three orders of magnitude. On the other hand, via the exchange of carotenoid, light absorption in the visible range can be tuned. These results show how in a relatively simple self-assembling pigment-polypeptide system a sophisticated functional tuning can be achieved and thus they provide guidelines for the construction of bio-inspired photoactive nanodevices.
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Ma F, Yu LJ, Ma XH, Wang P, Wang-Otomo ZY, Zhang JP. Bacterial Light-Harvesting Complexes Showing Giant Second-Order Nonlinear Optical Response as Revealed by Hyper-Rayleigh Light Scattering. J Phys Chem B 2016; 120:9395-401. [DOI: 10.1021/acs.jpcb.6b07461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fei Ma
- Department
of Chemistry, Renmin University of China, Beijing 1000872, P. R. China
| | - Long-Jiang Yu
- Faculty
of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan
| | - Xiao-Hua Ma
- Department
of Chemistry, Renmin University of China, Beijing 1000872, P. R. China
| | - Peng Wang
- Department
of Chemistry, Renmin University of China, Beijing 1000872, P. R. China
| | | | - Jian-Ping Zhang
- Department
of Chemistry, Renmin University of China, Beijing 1000872, P. R. China
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Harris MA, Sahin T, Jiang J, Vairaprakash P, Parkes-Loach PS, Niedzwiedzki DM, Kirmaier C, Loach PA, Bocian DF, Holten D, Lindsey JS. Enhanced Light-Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1-like Antennas. Photochem Photobiol 2014; 90:1264-76. [DOI: 10.1111/php.12319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 07/11/2014] [Indexed: 01/05/2023]
Affiliation(s)
| | - Tuba Sahin
- Department of Chemistry; North Carolina State University; Raleigh NC
| | - Jianbing Jiang
- Department of Chemistry; North Carolina State University; Raleigh NC
| | | | | | | | | | - Paul A. Loach
- Department of Molecular Biosciences; Northwestern University; Evanston IL
| | - David F. Bocian
- Department of Chemistry; University of California; Riverside CA
| | - Dewey Holten
- Department of Chemistry; Washington University; St. Louis MO
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Harris MA, Jiang J, Niedzwiedzki DM, Jiao J, Taniguchi M, Kirmaier C, Loach PA, Bocian DF, Lindsey JS, Holten D, Parkes-Loach PS. Versatile design of biohybrid light-harvesting architectures to tune location, density, and spectral coverage of attached synthetic chromophores for enhanced energy capture. PHOTOSYNTHESIS RESEARCH 2014; 121:35-48. [PMID: 24604033 DOI: 10.1007/s11120-014-9993-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 02/22/2014] [Indexed: 06/03/2023]
Abstract
Biohybrid antennas built upon chromophore-polypeptide conjugates show promise for the design of efficient light-capturing modules for specific purposes. Three new designs, each of which employs analogs of the β-polypeptide from Rhodobacter sphaeroides, have been investigated. In the first design, amino acids at seven different positions on the polypeptide were individually substituted with cysteine, to which a synthetic chromophore (bacteriochlorin or Oregon Green) was covalently attached. The polypeptide positions are at -2, -6, -10, -14, -17, -21, and -34 relative to the 0-position of the histidine that coordinates bacteriochlorophyll a (BChl a). All chromophore-polypeptides readily formed LH1-type complexes upon combination with the α-polypeptide and BChl a. Efficient energy transfer occurs from the attached chromophore to the circular array of 875 nm absorbing BChl a molecules (denoted B875). In the second design, use of two attachment sites (positions -10 and -21) on the polypeptide affords (1) double the density of chromophores per polypeptide and (2) a highly efficient energy-transfer relay from the chromophore at -21 to that at -10 and on to B875. In the third design, three spectrally distinct bacteriochlorin-polypeptides were prepared (each attached to cysteine at the -14 position) and combined in an ~1:1:1 mixture to form a heterogeneous mixture of LH1-type complexes with increased solar coverage and nearly quantitative energy transfer from each bacteriochlorin to B875. Collectively, the results illustrate the great latitude of the biohybrid approach for the design of diverse light-harvesting systems.
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Affiliation(s)
- Michelle A Harris
- Department of Chemistry, Washington University, St. Louis, MO, 63130-4889, USA
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Pandit A, de Groot HJM. Solid-state NMR applied to photosynthetic light-harvesting complexes. PHOTOSYNTHESIS RESEARCH 2012; 111:219-226. [PMID: 21842288 PMCID: PMC3295999 DOI: 10.1007/s11120-011-9674-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 07/12/2011] [Indexed: 05/29/2023]
Abstract
This short review describes how solid-state NMR has provided a mechanistic and electronic picture of pigment-protein and pigment-pigment interactions in photosynthetic antenna complexes. NMR results on purple bacterial antenna complexes show how the packing of the protein and the pigments inside the light-harvesting oligomers induces mutual conformational stress. The protein scaffold produces deformation and electrostatic polarization of the BChl macrocycles and leads to a partial electronic charge transfer between the BChls and their coordinating histidines, which can tune the light-harvesting function. In chlorosome antennae assemblies, the NMR template structure reveals how the chromophores can direct their self-assembly into higher macrostructures which, in turn, tune the light-harvesting properties of the individual molecules by controlling their disorder, structural deformation, and electronic polarization without the need for a protein scaffold. These results pave the way for addressing the next challenge, which is to resolve the functional conformational dynamics of the lhc antennae of oxygenic species that allows them to switch between light-emitting and light-energy dissipating states.
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Affiliation(s)
- Anjali Pandit
- Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Huub J. M. de Groot
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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Pandit A, Buda F, van Gammeren AJ, Ganapathy S, de Groot HJM. Selective Chemical Shift Assignment of Bacteriochlorophyll a in Uniformly [13C−15N]-Labeled Light-Harvesting 1 Complexes by Solid-State NMR in Ultrahigh Magnetic Field. J Phys Chem B 2010; 114:6207-15. [DOI: 10.1021/jp100688u] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anjali Pandit
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Francesco Buda
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Adriaan J. van Gammeren
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Swapna Ganapathy
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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10
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Structure-Function Relationships in Bacterial Light-Harvesting Complexes Investigated by Reconstitution Techniques. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-1-4020-8815-5_10] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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11
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Suzuki H, Shimada Y, Kobayashi M, Kudo M, Nozawa T, Wang ZY. Isotopic labeling of proteins by utilizing photosynthetic bacteria. Anal Biochem 2005; 347:324-6. [PMID: 16259936 DOI: 10.1016/j.ab.2005.05.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Revised: 05/11/2005] [Accepted: 05/12/2005] [Indexed: 11/24/2022]
Affiliation(s)
- Hiroaki Suzuki
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
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12
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Umetsu M, Kadota T, Wang ZY, Tanaka Y, Adschiri T, Nozawa T. Selective Detection of the Solid-state NMR Signals from the BacteriochlorophyllaDimers in a Reconstituted Light-harvesting 1 Complex. CHEM LETT 2005. [DOI: 10.1246/cl.2005.940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Fiedor L, Scheer H. Trapping of an assembly intermediate of photosynthetic LH1 antenna beyond B820 subunit. Significance for the assembly of photosynthetic LH1 antenna. J Biol Chem 2005; 280:20921-6. [PMID: 15788392 DOI: 10.1074/jbc.m501212200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most photosynthetic LH1 antennae undergo dissociation into B820 subunits, suggesting their universal character as structural modules. However, dissociation into subunits seems to occur reversibly only in the absence of carotenoids and the subunits were never found to bind carotenoids. The interactions of carotenoids with B820 have been studied in a newly developed reconstitution assay of the LH1 antenna from Rhodospirillum rubrum (Fiedor, L., Akahane, J., and Koyama, Y. (2004) Biochemistry 43, 16487-16496). These model studies show that B820 subunits strongly interact with carotenoids and spontaneously form stable LH1-like complexes with substoichiometric carotenoid content. This is the first experimental evidence that B820 may occur as a short-lived intermediate in the assembly of LH1 in vivo. The resulting complex of B820 subunits with carotenoid, termed iB873, is homogeneous, according to ion exchange chromatography and reproducible pigment composition. The iB873-bound carotenoid is as efficient in energy transfer to bacteriochlorophyll as the one in native antenna. To our knowledge, iB873 is the first complex binding functional carotenoid, with the spectral and biochemical properties intermediate between that of B820 and the fully assembled LH1.
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Affiliation(s)
- Leszek Fiedor
- Faculty of Biotechnology, Jagiellonian University, PL-30387 Cracow, Poland.
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Wang ZY, Gokan K, Kobayashi M, Nozawa T. Solution Structures of the Core Light-harvesting α and β Polypeptides from Rhodospirillum rubrum: Implications for the Pigment–Protein and Protein–Protein Interactions. J Mol Biol 2005; 347:465-77. [PMID: 15740753 DOI: 10.1016/j.jmb.2005.01.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2004] [Revised: 12/21/2004] [Accepted: 01/04/2005] [Indexed: 11/25/2022]
Abstract
We have determined the solution structures of the core light-harvesting (LH1) alpha and beta-polypeptides from wild-type purple photosynthetic bacterium Rhodospirillum rubrum using multidimensional NMR spectroscopy. The two polypeptides form stable alpha helices in organic solution. The structure of alpha-polypeptide consists of a long helix of 32 amino acid residues over the central transmembrane domain and a short helical segment at the N terminus that is followed by a three-residue loop. Pigment-coordinating histidine residue (His29) in the alpha-polypeptide is located near the middle of the central helix. The structure of beta-polypeptide shows a single helix of 32 amino acid residues in the membrane-spanning region with the pigment-coordinating histidine residue (His38) at a position close to the C-terminal end of the helix. Strong hydrogen bonds have been identified for the backbone amide protons over the central helical regions, indicating a rigid property of the two polypeptides. The overall structures of the R.rubrum LH1 alpha and beta-polypeptides are different from those previously reported for the LH1 beta-polypeptide of Rhodobacter sphaeroides, but are very similar to the structures of the corresponding LH2 alpha and beta-polypeptides determined by X-ray crystallography. A model constructed for the structural subunit (B820) of LH1 complex using the solution structures reveals several important features on the interactions between the LH1 alpha and beta-polypeptides. The significance of the N-terminal regions of the two polypeptides for stabilizing both B820 and LH1 complexes, as clarified by many experiments, may be attributed to the interactions between the short N-terminal helix (Trp2-Gln6) of alpha-polypeptide and a GxxxG motif in the beta-polypeptide.
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Affiliation(s)
- Zheng-Yu Wang
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aramaki-aza, Aoba, Aoba-ku, Sendai 980-8579, Japan.
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Morishita H, Tamiaki H. Synthesis of 18O-Labelled chlorophyll derivatives at carbonyl oxygen atoms by acidic hydrolysis of the ethylene ketal and acetal. Bioorg Med Chem 2003; 11:4049-57. [PMID: 12927867 DOI: 10.1016/s0968-0896(03)00335-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The ethylene ketal of pyropheophorbides, chlorophylls possessing the 13-keto carbonyl group and lacking the 13(2)-methoxycarbonyl group, reacted with H(2)(18)O (ca. 95% 18O atom) by acidic hydrolysis to give efficiently and regioselectively 13(1)-18O-oxo-labelled compounds (ca. 92% 18O). The resulting 18O-labelled chlorin was modified by several chemical reactions to afford some derivatives with little loss of the 18O atom. Following the same procedures, 3(1),13(1)-doubly-18O-labelled pyrochlorophyll derivatives were also prepared. All the synthetic 18O-labelled compounds were identified by FAB-mass and vibrational spectra. Especially, in the vibrational spectroscopic results including IR and resonance Raman spectra, an about 30 cm(-1) wavenumber down-shift of the 3- and/or 13-C[double bond]O stretching vibrational bands was observed by exchanging 3(1)- or 13(1)-oxo-oxygen atom from 16O to 18O.
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Affiliation(s)
- Hidetada Morishita
- Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan
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Wang ZY, Shimonaga M, Kobayashi M, Nozawa T. N-terminal methylation of the core light-harvesting complex in purple photosynthetic bacteria. FEBS Lett 2002; 519:164-8. [PMID: 12023037 DOI: 10.1016/s0014-5793(02)02744-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Several core light-harvesting complexes from both sulfur and non-sulfur purple photosynthetic bacteria have been identified to be methylated at the N-terminal alpha-amino group of beta-polypeptides by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance. Monomethylation has been confirmed for the N-terminal alanine residues of the beta-polypeptides from Rhodospirillum rubrum, Thermochromatium tepidum and Chromatium vinosum, but not for the beta-polypeptide from Rhodobacter sphaeroides. The modification appears to be related with the amino acid sequence and charge distribution in the N-terminal end. Some common features and possible functions are discussed.
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Affiliation(s)
- Zheng Yu Wang
- Department of Biomolecular Engineering, Faculty of Engineering, Center for Interdisciplinary Research, Tohoku University, Sendai, Japan.
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