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Guo R, Wang S, Niu NN, Xu YL, Zhu JX, Scheer H, Noy D, Zhao KH. Dichromic Allophycocyanin Trimer Covering a Broad Spectral Range (550-660 nm). Chemistry 2023; 29:e202203367. [PMID: 36382427 DOI: 10.1002/chem.202203367] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/17/2022]
Abstract
Phycobilisomes, the light-harvesting complexes of cyanobacteria and red algae, are a resource for photosynthetic, photonic and fluorescence labeling elements. They cover an exceptionally broad spectral range, but the complex superstructure and assembly have been an obstacle. By replacing in Synechocystis sp. PCC 6803 the biliverdin reductases, we studied the role of chromophores in the assembly of the phycobilisome core. Introduction of the green-absorbing phycoerythrobilin instead of the red-absorbing phycocyanobilin inhibited aggregation. A novel, trimeric allophycocyanin (Dic-APC) was obtained. In the small (110 kDa) unit, the two chromophores, phycoerythrobilin and phytochromobilin, cover a wide spectral range (550 to 660 nm). Due to efficient energy transfer, it provides an efficient artificial light-harvesting element. Dic-APC was generated in vitro by using the contained core-linker, LC , for template-assisted purification and assembly. Labeling the linker provides a method for targeting Dic-APC.
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Affiliation(s)
- Rui Guo
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Si Wang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Nan-Nan Niu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Ya-Li Xu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Jun-Xun Zhu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
| | - Hugo Scheer
- Department Biologie I, Universität München, Menzinger Str. 67, D-80638, München, Germany
| | - Dror Noy
- MIGAL-Galilee Research Institute S. Industrial Zone, Kiryat Shmona, Israel.,Faculty of Sciences and Technology, Tel-Hai Academic College, Upper Galilee, Israel
| | - Kai-Hong Zhao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, P.R. China
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2
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Joutsuka T, Nanasawa R, Igarashi K, Horie K, Sugishima M, Hagiwara Y, Wada K, Fukuyama K, Yano N, Mori S, Ostermann A, Kusaka K, Unno M. Neutron crystallography and quantum chemical analysis of bilin reductase PcyA mutants reveal substrate and catalytic residue protonation states. J Biol Chem 2022; 299:102763. [PMID: 36463961 PMCID: PMC9800206 DOI: 10.1016/j.jbc.2022.102763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 11/16/2022] [Accepted: 11/29/2022] [Indexed: 12/04/2022] Open
Abstract
PcyA, a ferredoxin-dependent bilin pigment reductase, catalyzes the site-specific reduction of the two vinyl groups of biliverdin (BV), producing phycocyanobilin. Previous neutron crystallography detected both the neutral BV and its protonated form (BVH+) in the wildtype (WT) PcyA-BV complex, and a nearby catalytic residue Asp105 was found to have two conformations (protonated and deprotonated). Semiempirical calculations have suggested that the protonation states of BV are reflected in the absorption spectrum of the WT PcyA-BV complex. In the previously determined absorption spectra of the PcyA D105N and I86D mutants, complexed with BV, a peak at 730 nm, observed in the WT, disappeared and increased, respectively. Here, we performed neutron crystallography and quantum chemical analysis of the D105N-BV and I86D-BV complexes to determine the protonation states of BV and the surrounding residues and study the correlation between the absorption spectra and protonation states around BV. Neutron structures elucidated that BV in the D105N mutant is in a neutral state, whereas that in the I86D mutant is dominantly in a protonated state. Glu76 and His88 showed different hydrogen bonding with surrounding residues compared with WT PcyA, further explaining why D105N and I86D have much lower activities for phycocyanobilin synthesis than the WT PcyA. Our quantum mechanics/molecular mechanics calculations of the absorption spectra showed that the spectral change in D105N arises from Glu76 deprotonation, consistent with the neutron structure. Collectively, our findings reveal more mechanistic details of bilin pigment biosynthesis.
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Affiliation(s)
- Tatsuya Joutsuka
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan,Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan,For correspondence: Tatsuya Joutsuka; Masaki Unno
| | - Ryota Nanasawa
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan
| | - Keisuke Igarashi
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan
| | - Kazuki Horie
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan
| | - Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka, Japan
| | - Yoshinori Hagiwara
- Department of Biochemistry and Applied Chemistry, National Institute of Technology, Kurume College, Kurume, Fukuoka, Japan
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki, Miyazaki, Japan
| | - Keiichi Fukuyama
- Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Naomine Yano
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan
| | - Seiji Mori
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan,Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan
| | - Andreas Ostermann
- Heinz Maier-Leibnitz Zentrum (MLZ), Technical University Munich, Garching, Germany
| | - Katsuhiro Kusaka
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan
| | - Masaki Unno
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan,Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan,For correspondence: Tatsuya Joutsuka; Masaki Unno
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3
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Identification of significant residues for intermediate accumulation in phycocyanobilin synthesis. Photochem Photobiol Sci 2022; 21:437-446. [PMID: 35394642 DOI: 10.1007/s43630-022-00198-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 02/28/2022] [Indexed: 10/18/2022]
Abstract
Phycocyanobilin, the primary pigment of both light perception and light-harvesting in cyanobacteria, is synthesized from biliverdin IXα (BV) through intermediate 181, 182-dihydrobiliverdin (181, 182-DHBV) by a phycocyanobilin:ferredoxin oxidoreductase (PcyA). In our previous study, we discovered two PcyA homologs (AmPcyAc and AmPcyAp) derived from Acaryochloris marina MBIC 11017 (A. marina) that exceptionally uses chlorophyll d as the primary photosynthetic pigment, absorbing longer wavelength far-red light than chlorophyll a, the photosynthetic pigment found in most cyanobacteria. Biochemical characterization of the two PcyA homologs identified functional diversification of these two enzymes: AmPcyAc provides 181, 182-DHBV, and PCB to the cyanobacteriochrome (CBCR) photoreceptors, whereas, AmPcyAp specifically provides PCB to the light-harvesting phycobilisome subunit. In this study, we focused on the residues necessary for 181, 182-DHBV supply to the CBCR photoreceptors by AmPcyAc. Based on the SyPcyA structure, we concentrated on the 30 residues that constitute the substrate-binding pocket. Among them, we discovered that Leu151 and Val225 in AmPcyAc were both substituted with isoleucine. During the enzymatic reaction, the SyPcyA variant molecule, possessing V225I and L151I replacements, accumulates the 181, 182-DHBV and supplies it to a CBCR molecule derived from A. marina. It is worth noting that the substitution of Val225 with isoleucine was specifically conserved among the Acaryochloris genus. Collectively, we propose that the specific evolution of PcyA among the Acaryochloris genus may correlate with the acquisition of Chl. d synthetic ability and growth in long-wavelength far-red light environments.
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Piao M, Zou J, Li Z, Zhang J, Yang L, Yao N, Li Y, Li Y, Tang H, Zhang L, Yang D, Yang Z, Du X, Zuo Z. The Arabidopsis HY2 Gene Acts as a Positive Regulator of NaCl Signaling during Seed Germination. Int J Mol Sci 2021; 22:ijms22169009. [PMID: 34445714 PMCID: PMC8396667 DOI: 10.3390/ijms22169009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 07/30/2021] [Accepted: 08/17/2021] [Indexed: 11/16/2022] Open
Abstract
Phytochromobilin (PΦB) participates in the regulation of plant growth and development as an important synthetase of photoreceptor phytochromes (phy). In addition, Arabidopsis long hypocotyl 2 (HY2) appropriately works as a key PΦB synthetase. However, whether HY2 takes part in the plant stress response signal network remains unknown. Here, we described the function of HY2 in NaCl signaling. The hy2 mutant was NaCl-insensitive, whereas HY2-overexpressing lines showed NaCl-hypersensitive phenotypes during seed germination. The exogenous NaCl induced the transcription and the protein level of HY2, which positively mediated the expression of downstream stress-related genes of RD29A, RD29B, and DREB2A. Further quantitative proteomics showed the patterns of 7391 proteins under salt stress. HY2 was then found to specifically mediate 215 differentially regulated proteins (DRPs), which, according to GO enrichment analysis, were mainly involved in ion homeostasis, flavonoid biosynthetic and metabolic pathways, hormone response (SA, JA, ABA, ethylene), the reactive oxygen species (ROS) metabolic pathway, photosynthesis, and detoxification pathways to respond to salt stress. More importantly, ANNAT1–ANNAT2–ANNAT3–ANNAT4 and GSTU19–GSTF10–RPL5A–RPL5B–AT2G32060, two protein interaction networks specifically regulated by HY2, jointly participated in the salt stress response. These results direct the pathway of HY2 participating in salt stress, and provide new insights for the plant to resist salt stress.
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Affiliation(s)
- Mingxin Piao
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Jinpeng Zou
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
- College of Agriculture, Northeast Agricultural University, Harbin 150030, China;
| | - Zhifang Li
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Junchuan Zhang
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Liang Yang
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Nan Yao
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Yuhong Li
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Yaxing Li
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Haohao Tang
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Li Zhang
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
| | - Deguang Yang
- College of Agriculture, Northeast Agricultural University, Harbin 150030, China;
| | - Zhenming Yang
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
| | - Xinglin Du
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
- Correspondence: (X.D.); (Z.Z.)
| | - Zecheng Zuo
- Jilin Province Engineering Laboratory of Plant Genetic Improvement, College of Plant Science, Jilin University, Changchun 130062, China; (M.P.); (J.Z.); (L.Y.); (L.Z.); (Z.Y.)
- Basic Forestry and Proteomics Research Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (J.Z.); (Z.L.); (N.Y.); (Y.L.); (Y.L.); (H.T.)
- Correspondence: (X.D.); (Z.Z.)
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Koehl P, Delarue M, Orland H. Simultaneous Identification of Multiple Binding Sites in Proteins: A Statistical Mechanics Approach. J Phys Chem B 2021; 125:5052-5067. [PMID: 33973782 DOI: 10.1021/acs.jpcb.1c02658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present an extension of the Poisson-Boltzmann model in which the solute of interest is immersed in an assembly of self-orienting Langevin water dipoles, anions, cations, and hydrophobic molecules, all of variable densities. Interactions between charges are controlled by electrostatics, while hydrophobic interactions are modeled with a Yukawa potential. We impose steric constraints by assuming that the system is represented on a cubic lattice. We also assume incompressibility; i.e., all sites of the lattice are occupied. This model, which we refer to as the Hydrophobic Dipolar Poisson-Boltzmann Langevin (HDPBL) model, leads to a system of two equations whose solutions give the water dipole, salt, and hydrophobic molecule densities, all of them in the presence of the others in a self-consistent way. We use those to study the organization of the ions, cosolvent, and solvent molecules around proteins. In particular, peaks of densities are expected to reveal, simultaneously, the presence of compatible binding sites of different kinds on a protein. We have tested and validated the ability of HDPBL to detect pockets in proteins that bind to hydrophobic ligands, polar ligands, and charged small probes as well as to characterize the binding sites of lipids for membrane proteins.
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Affiliation(s)
- Patrice Koehl
- Department of Computer Science and Genome Center, University of California, Davis, California 95616, United States
| | - Marc Delarue
- Architecture et Dynamique des Macromolécules Biologiques, Département de Biologie Structurale et Chimie, UMR 3528 du CNRS, Institut Pasteur, 75015 Paris, France
| | - Henri Orland
- Institut de Physique Théorique, Université Paris-Saclay, CEA, 91191 Gif/Yvette Cedex, France
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6
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Sugishima M, Wada K, Fukuyama K, Yamamoto K. Crystal structure of phytochromobilin synthase in complex with biliverdin IXα, a key enzyme in the biosynthesis of phytochrome. J Biol Chem 2020; 295:771-782. [PMID: 31822504 DOI: 10.1074/jbc.ra119.011431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/08/2019] [Indexed: 11/06/2022] Open
Abstract
Phytochromobilin (PΦB) is a red/far-red light sensory pigment in plant phytochrome. PΦB synthase is a ferredoxin-dependent bilin reductase (FDBR) that catalyzes the site-specific reduction of bilins, which are sensory and photosynthesis pigments, and produces PΦB from biliverdin, a heme-derived linear tetrapyrrole pigment. Here, we determined the crystal structure of tomato PΦB synthase in complex with biliverdin at 1.95 Å resolution. The overall structure of tomato PΦB synthase was similar to those of other FDBRs, except for the addition of a long C-terminal loop and short helices. The structure further revealed that the C-terminal loop is part of the biliverdin-binding pocket and that two basic residues in the C-terminal loop form salt bridges with the propionate groups of biliverdin. This suggested that the C-terminal loop is involved in the interaction with ferredoxin and biliverdin. The configuration of biliverdin bound to tomato PΦB synthase differed from that of biliverdin bound to other FDBRs, and its orientation in PΦB synthase was inverted relative to its orientation in the other FDBRs. Structural and enzymatic analyses disclosed that two aspartic acid residues, Asp-123 and Asp-263, form hydrogen bonds with water molecules and are essential for the site-specific A-ring reduction of biliverdin. On the basis of these observations and enzymatic assays with a V121A PΦB synthase variant, we propose the following mechanistic product release mechanism: PΦB synthase-catalyzed stereospecific reduction produces 2(R)-PΦB, which when bound to PΦB synthase collides with the side chain of Val-121, releasing 2(R)-PΦB from the synthase.
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Affiliation(s)
- Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Ken Yamamoto
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
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7
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Sugishima M, Wada K, Fukuyama K, Yamamoto K. Crystal structure of phytochromobilin synthase in complex with biliverdin IXα, a key enzyme in the biosynthesis of phytochrome. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49934-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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8
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Sommerkamp JA, Frankenberg-Dinkel N, Hofmann E. Crystal structure of the first eukaryotic bilin reductase GtPEBB reveals a flipped binding mode of dihydrobiliverdin. J Biol Chem 2019; 294:13889-13901. [PMID: 31366727 PMCID: PMC6755814 DOI: 10.1074/jbc.ra119.009306] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 07/26/2019] [Indexed: 01/11/2023] Open
Abstract
Phycobilins are light-harvesting pigments of cyanobacteria, red algae, and cryptophytes. The biosynthesis of phycoerythrobilin (PEB) is catalyzed by the subsequent action of two ferredoxin-dependent bilin reductases (FDBRs). Although 15,16-dihydrobiliverdin (DHBV):ferredoxin oxidoreductase (PebA) catalyzes the two-electron reduction of biliverdin IXα to 15,16-DHBV, PEB:ferredoxin oxidoreductase (PebB) reduces this intermediate further to PEB. Interestingly, marine viruses encode the FDBR PebS combining both activities within one enzyme. Although PebA and PebS share a canonical fold with similar substrate-binding pockets, the structural determinants for the stereo- and regiospecific modification of their tetrapyrrole substrates are incompletely understood, also because of the lack of a PebB structure. Here, we solved the X-ray crystal structures of both substrate-free and -bound PEBB from the cryptophyte Guillardia theta at 1.90 and 1.65 Å, respectively. The structures of PEBB exhibit the typical α/β/α-sandwich fold. Interestingly, the open-chain tetrapyrrole substrate DHBV is bound in an unexpected flipped orientation within the canonical FDBR active site. Biochemical analyses of the WT enzyme and active site variants identified two central aspartate residues Asp-99 and Asp-219 as essential for catalytic activity. In addition, the conserved Arg-215 plays a critical role in substrate specificity, binding orientation, and active site integrity. Because these critical residues are conserved within certain FDBRs displaying A-ring reduction activity, we propose that they present a conserved mechanism for this reaction. The flipped substrate-binding mode indicates that two-electron reducing FDBRs utilize the same primary site within the binding pocket and that substrate orientation is the determinant for A- or D-ring regiospecificity.
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Affiliation(s)
- Johannes A Sommerkamp
- Protein Crystallography, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nicole Frankenberg-Dinkel
- Department of Biology, Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Eckhard Hofmann
- Protein Crystallography, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44801 Bochum, Germany
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Aras M, Hartmann V, Hartmann J, Nowaczyk MM, Frankenberg-Dinkel N. Proximity channeling during cyanobacterial phycoerythrobilin synthesis. FEBS J 2019; 287:284-294. [PMID: 31319014 DOI: 10.1111/febs.15003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 06/17/2019] [Accepted: 07/16/2019] [Indexed: 11/30/2022]
Abstract
Substrate channeling is a widespread mechanism in metabolic pathways to avoid decomposition of unstable intermediates, competing reactions, and to accelerate catalytic turnover. During the biosynthesis of light-harvesting phycobilins in cyanobacteria, two members of the ferredoxin-dependent bilin reductases are involved in the reduction of the open-chain tetrapyrrole biliverdin IXα to the pink pigment phycoerythrobilin. The first reaction is catalyzed by 15,16-dihydrobiliverdin:ferredoxin oxidoreductase and produces the unstable intermediate 15,16-dihydrobiliverdin (DHBV). This intermediate is subsequently converted by phycoerythrobilin:ferredoxin oxidoreductase to the final product phycoerythrobilin. Although substrate channeling has been postulated already a decade ago, detailed experimental evidence was missing. Using a new on-column assay employing immobilized enzyme in combination with UV-Vis and fluorescence spectroscopy revealed that both enzymes transiently interact and that transfer of the intermediate is facilitated by a significantly higher binding affinity of DHBV toward phycoerythrobilin:ferredoxin oxidoreductase. Concluding from the presented data, the intermediate DHBV is transferred via proximity channeling.
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Affiliation(s)
- Marco Aras
- Fachbereich Biologie, Abteilung für Mikrobiologie, Technische Universität Kaiserslautern, Germany
| | - Volker Hartmann
- Cyanobakterielle Membranprotein Komplexe, Fakultät für Biologie und Biotechnologie, Ruhr-Universität Bochum, Germany
| | - Jana Hartmann
- Fachbereich Biologie, Abteilung für Mikrobiologie, Technische Universität Kaiserslautern, Germany
| | - Marc M Nowaczyk
- Cyanobakterielle Membranprotein Komplexe, Fakultät für Biologie und Biotechnologie, Ruhr-Universität Bochum, Germany
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Sugishima M, Wada K, Unno M, Fukuyama K. Bilin-metabolizing enzymes: site-specific reductions catalyzed by two different type of enzymes. Curr Opin Struct Biol 2019; 59:73-80. [PMID: 30954759 DOI: 10.1016/j.sbi.2019.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 01/09/2019] [Accepted: 03/04/2019] [Indexed: 02/05/2023]
Abstract
In mammals, the green heme metabolite biliverdin is converted to a yellow anti-oxidant by NAD(P)H-dependent biliverdin reductase (BVR), whereas in O2-dependent photosynthetic organisms it is converted to photosynthetic or light-sensing pigments by ferredoxin-dependent bilin reductases (FDBRs). In NADP+-bound and biliverdin-bound BVR-A, two biliverdins are stacked at the binding cleft; one is positioned to accept hydride from NADPH, and the other appears to donate a proton to the first biliverdin through a neighboring arginine residue. During the FDBR-catalyzed reaction, electrons and protons are supplied to bilins from ferredoxin and from FDBRs and waters bound within FDBRs, respectively. Thus, the protonation sites of bilin and catalytic residues are important for the analysis of site-specific reduction. The neutron structure of FDBR sheds light on this issue.
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Affiliation(s)
- Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan.
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Masaki Unno
- Graduate School of Science and Engineering, Ibaraki University, Ibaraki 316-8511, Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
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11
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Ledermann B, Schwan M, Sommerkamp JA, Hofmann E, Béjà O, Frankenberg-Dinkel N. Evolution and molecular mechanism of four-electron reducing ferredoxin-dependent bilin reductases from oceanic phages. FEBS J 2017; 285:339-356. [PMID: 29156487 DOI: 10.1111/febs.14341] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 11/06/2017] [Accepted: 11/16/2017] [Indexed: 01/17/2023]
Abstract
Ferredoxin-dependent bilin reductases (FDBRs) are a class of enzymes reducing the heme metabolite biliverdin IXα (BV) to form open-chain tetrapyrroles used for light-perception and light-harvesting in photosynthetic organisms. Thus far, seven FDBR families have been identified, each catalysing a distinct reaction and either transferring two or four electrons from ferredoxin onto the substrate. The newest addition to the family is PcyX, originally identified from metagenomics data derived from phage. Phylogenetically, PcyA is the closest relative catalysing the reduction of BV to phycocyanobilin. PcyX, however, converts the same substrate to phycoerythrobilin, resembling the reaction catalysed by cyanophage PebS. Within this study, we aimed at understanding the evolution of catalytic activities within FDBRs using PcyX as an example. Additional members of the PcyX clade and a remote member of the PcyA family were investigated to gain insights into catalysis. Biochemical data in combination with the PcyX crystal structure revealed that a conserved aspartate-histidine pair is critical for activity. Interestingly, the same residues are part of a catalytic Asp-His-Glu triad in PcyA, including an additional Glu. While this Glu residue is replaced by Asp in PcyX, it is not involved in catalysis. Substitution back to a Glu failed to convert PcyX to a PcyA. Therefore, the change in regiospecificity is not only caused by individual catalytic amino acid residues. Rather the combination of the architecture of the active site with the positioning of the substrate triggers specific proton transfer yielding the individual phycobilin products. ENZYMES Suggested EC number for PcyX: 1.3.7.6 DATABASES: The PcyX X-ray structure was deposited in the PDB with the accession code 5OWG.
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Affiliation(s)
- Benjamin Ledermann
- Department of Biology, Microbiology, Technical University Kaiserslautern, Germany
| | - Meike Schwan
- Department of Biology, Microbiology, Technical University Kaiserslautern, Germany
| | - Johannes A Sommerkamp
- Protein Crystallography, Faculty for Biology and Biotechnology, Ruhr University Bochum, Germany
| | - Eckhard Hofmann
- Protein Crystallography, Faculty for Biology and Biotechnology, Ruhr University Bochum, Germany
| | - Oded Béjà
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa, Israel
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12
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Rockwell NC, Martin SS, Li FW, Mathews S, Lagarias JC. The phycocyanobilin chromophore of streptophyte algal phytochromes is synthesized by HY2. THE NEW PHYTOLOGIST 2017; 214:1145-1157. [PMID: 28106912 PMCID: PMC5388591 DOI: 10.1111/nph.14422] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 12/04/2016] [Indexed: 05/11/2023]
Abstract
Land plant phytochromes perceive red and far-red light to control growth and development, using the linear tetrapyrrole (bilin) chromophore phytochromobilin (PΦB). Phytochromes from streptophyte algae, sister species to land plants, instead use phycocyanobilin (PCB). PCB and PΦB are synthesized by different ferredoxin-dependent bilin reductases (FDBRs): PΦB is synthesized by HY2, whereas PCB is synthesized by PcyA. The pathway for PCB biosynthesis in streptophyte algae is unknown. We used phylogenetic analysis and heterologous reconstitution of bilin biosynthesis to investigate bilin biosynthesis in streptophyte algae. Phylogenetic results suggest that PcyA is present in chlorophytes and prasinophytes but absent in streptophytes. A system reconstituting bilin biosynthesis in Escherichia coli was modified to utilize HY2 from the streptophyte alga Klebsormidium flaccidum (KflaHY2). The resulting bilin was incorporated into model cyanobacterial photoreceptors and into phytochrome from the early-diverging streptophyte alga Mesostigma viride (MvirPHY1). All photoreceptors tested incorporate PCB rather than PΦB, indicating that KflaHY2 is sufficient for PCB synthesis without any other algal protein. MvirPHY1 exhibits a red-far-red photocycle similar to those seen in other streptophyte algal phytochromes. These results demonstrate that streptophyte algae use HY2 to synthesize PCB, consistent with the hypothesis that PΦB synthesis arose late in HY2 evolution.
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Affiliation(s)
- Nathan C. Rockwell
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Shelley S. Martin
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Fay-Wei Li
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Sarah Mathews
- CSIRO National Research Collections Australia, Australian National Herbarium, Canberra, ACT, 2601, Australia
| | - J. Clark Lagarias
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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13
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Gasper R, Schwach J, Hartmann J, Holtkamp A, Wiethaus J, Riedel N, Hofmann E, Frankenberg-Dinkel N. Distinct Features of Cyanophage-encoded T-type Phycobiliprotein Lyase ΦCpeT: THE ROLE OF AUXILIARY METABOLIC GENES. J Biol Chem 2017; 292:3089-3098. [PMID: 28073912 DOI: 10.1074/jbc.m116.769703] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/03/2017] [Indexed: 11/06/2022] Open
Abstract
Auxiliary metabolic genes (AMG) are commonly found in the genomes of phages that infect cyanobacteria and increase the fitness of the cyanophage. AMGs are often homologs of host genes, and also typically related to photosynthesis. For example, the ΦcpeT gene in the cyanophage P-HM1 encodes a putative phycobiliprotein lyase related to cyanobacterial T-type lyases, which facilitate attachment of linear tetrapyrrole chromophores to Cys-155 of phycobiliprotein β-subunits, suggesting that ΦCpeT may also help assemble light-harvesting phycobiliproteins during infection. To investigate this possibility, we structurally and biochemically characterized recombinant ΦCpeT. The solved crystal structure of ΦCpeT at 1.8-Å resolution revealed that the protein adopts a similar fold as the cyanobacterial T-type lyase CpcT from Nostoc sp. PCC7120 but overall is more compact and smaller. ΦCpeT specifically binds phycoerythrobilin (PEB) in vitro leading to a tight complex that can also be formed in Escherichia coli when it is co-expressed with genes encoding PEB biosynthesis (i.e. ho1 and pebS). The formed ΦCpeT·PEB complex was very stable as the chromophore was not lost during chromatography and displayed a strong red fluorescence with a fluorescence quantum yield of ΦF = 0.3. This complex was not directly able to transfer PEB to the host phycobiliprotein β-subunit. However, it could assist the host lyase CpeS in its function by providing a pool of readily available PEB, a feature that might be important for fast phycobiliprotein assembly during phage infection.
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Affiliation(s)
| | - Julia Schwach
- Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum
| | - Jana Hartmann
- Department of Biology, Division for Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Andrea Holtkamp
- Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum
| | - Jessica Wiethaus
- Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum
| | - Natascha Riedel
- Department of Biology, Division for Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany
| | | | - Nicole Frankenberg-Dinkel
- Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum; Department of Biology, Division for Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany.
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14
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Hagiwara Y, Wada K, Irikawa T, Sato H, Unno M, Yamamoto K, Fukuyama K, Sugishima M. Atomic-resolution structure of the phycocyanobilin:ferredoxin oxidoreductase I86D mutant in complex with fully protonated biliverdin. FEBS Lett 2016; 590:3425-3434. [DOI: 10.1002/1873-3468.12387] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 08/28/2016] [Accepted: 08/31/2016] [Indexed: 02/05/2023]
Affiliation(s)
- Yoshinori Hagiwara
- Department of Biochemistry and Applied Chemistry; National Institute of Technology; Kurume College; Kurume Japan
| | - Kei Wada
- Organization for Promotion of Tenure Track; University of Miyazaki; Kiyotake Japan
| | - Teppei Irikawa
- Department of Biological Sciences; Graduate School of Science; Osaka University; Toyonaka Japan
| | - Hideaki Sato
- Department of Medical Biochemistry; Kurume University School of Medicine; Kurume Japan
| | - Masaki Unno
- Graduate School of Science and Engineering; Ibaraki University; Hitachi Japan
- Frontier Research Center for Applied Atomic Sciences; Ibaraki University; Naka Japan
| | - Ken Yamamoto
- Department of Medical Biochemistry; Kurume University School of Medicine; Kurume Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences; Graduate School of Science; Osaka University; Toyonaka Japan
- Department of Applied Chemistry; Graduate School of Engineering; Osaka University; Suita Japan
| | - Masakazu Sugishima
- Department of Medical Biochemistry; Kurume University School of Medicine; Kurume Japan
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15
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Ledermann B, Béjà O, Frankenberg-Dinkel N. New biosynthetic pathway for pink pigments from uncultured oceanic viruses. Environ Microbiol 2016; 18:4337-4347. [PMID: 26950653 DOI: 10.1111/1462-2920.13290] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 03/04/2016] [Indexed: 12/18/2022]
Abstract
The pink open-chain tetrapyrrole pigment phycoerythrobilin (PEB) is employed by marine cyanobacteria, red algae and cryptophytes as a light-harvesting chromophore in phycobiliproteins. Genes encoding biosynthesis proteins for PEB have also been discovered in cyanophages, viruses that infect cyanobacteria, and mimic host pigment biosynthesis with the exception of PebS which combines the enzymatic activities of two host enzymes. In this study, we have identified novel members of the PEB biosynthetic enzyme families, heme oxygenases and ferredoxin-dependent bilin reductases. Encoding genes were found in metagenomic datasets and could be traced back to bacteriophage but not cyanophage origin. While the heme oxygenase exhibited standard activity, a new bilin reductase with highest homology to the teal pigment producing enzyme PcyA revealed PEB biosynthetic activity. Although PcyX possesses PebS-like activity both enzymes share only 9% sequence identity and likely catalyze the reaction via two independent mechanisms. Our data point towards the presence of phycobilin biosynthetic genes in phages that probably infect alphaproteobacteria and, therefore, further support a role of phycobilins outside oxygenic phototrophs.
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Affiliation(s)
- Benjamin Ledermann
- Department of Biology, Microbiology, Technical University Kaiserslautern, Kaiserslautern, Germany
| | - Oded Béjà
- Technion-Israel Institute of Technology, Haifa, Israel
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16
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Kiesel S, Wätzlich D, Lange C, Reijerse E, Bröcker MJ, Rüdiger W, Lubitz W, Scheer H, Moser J, Jahn D. Iron-sulfur cluster-dependent catalysis of chlorophyllide a oxidoreductase from Roseobacter denitrificans. J Biol Chem 2015; 290:1141-54. [PMID: 25422320 PMCID: PMC4294481 DOI: 10.1074/jbc.m114.617761] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Revised: 11/18/2014] [Indexed: 11/06/2022] Open
Abstract
Bacteriochlorophyll a biosynthesis requires the stereo- and regiospecific two electron reduction of the C7-C8 double bond of chlorophyllide a by the nitrogenase-like multisubunit metalloenzyme, chlorophyllide a oxidoreductase (COR). ATP-dependent COR catalysis requires interaction of the protein subcomplex (BchX)2 with the catalytic (BchY/BchZ)2 protein to facilitate substrate reduction via two redox active iron-sulfur centers. The ternary COR enzyme holocomplex comprising subunits BchX, BchY, and BchZ from the purple bacterium Roseobacter denitrificans was trapped in the presence of the ATP transition state analog ADP·AlF4(-). Electron paramagnetic resonance experiments revealed a [4Fe-4S] cluster of subcomplex (BchX)2. A second [4Fe-4S] cluster was identified on (BchY/BchZ)2. Mutagenesis experiments indicated that the latter is ligated by four cysteines, which is in contrast to the three cysteine/one aspartate ligation pattern of the closely related dark-operative protochlorophyllide a oxidoreductase (DPOR). In subsequent mutagenesis experiments a DPOR-like aspartate ligation pattern was implemented for the catalytic [4Fe-4S] cluster of COR. Artificial cluster formation for this inactive COR variant was demonstrated spectroscopically. A series of chemically modified substrate molecules with altered substituents on the individual pyrrole rings and the isocyclic ring were tested as COR substrates. The COR enzyme was still able to reduce the B ring of substrates carrying modified substituents on ring systems A, C, and E. However, substrates with a modification of the distantly located propionate side chain were not accepted. A tentative substrate binding mode was concluded in analogy to the related DPOR system.
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Affiliation(s)
- Svenja Kiesel
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Denise Wätzlich
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Christiane Lange
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Edward Reijerse
- Max-Planck-Institute for Chemical Energy Conversion, D-45470 Mülheim, Germany
| | - Markus J Bröcker
- Department of Molecular Biophysics and Biochemistry, Yale University New Haven, Connecticut 06520, and
| | - Wolfhart Rüdiger
- Department Biology I, Botany, Ludwig-Maximilians-Universität München, D-80638 München, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institute for Chemical Energy Conversion, D-45470 Mülheim, Germany
| | - Hugo Scheer
- Department Biology I, Botany, Ludwig-Maximilians-Universität München, D-80638 München, Germany
| | - Jürgen Moser
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany,
| | - Dieter Jahn
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
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17
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18
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Overkamp KE, Gasper R, Kock K, Herrmann C, Hofmann E, Frankenberg-Dinkel N. Insights into the biosynthesis and assembly of cryptophycean phycobiliproteins. J Biol Chem 2014; 289:26691-26707. [PMID: 25096577 DOI: 10.1074/jbc.m114.591131] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Phycobiliproteins are employed by cyanobacteria, red algae, glaucophytes, and cryptophytes for light-harvesting and consist of apoproteins covalently associated with open-chain tetrapyrrole chromophores. Although the majority of organisms assemble the individual phycobiliproteins into larger aggregates called phycobilisomes, members of the cryptophytes use a single type of phycobiliprotein that is localized in the thylakoid lumen. The cryptophyte Guillardia theta (Gt) uses phycoerythrin PE545 utilizing the uncommon chromophore 15,16-dihydrobiliverdin (DHBV) in addition to phycoerythrobilin (PEB). Both the biosynthesis and the attachment of chromophores to the apophycobiliprotein have not yet been investigated for cryptophytes. In this study, we identified and characterized enzymes involved in PEB biosynthesis. In addition, we present the first in-depth biochemical characterization of a eukaryotic phycobiliprotein lyase (GtCPES). Plastid-encoded HO (GtHo) was shown to convert heme into biliverdin IXα providing the substrate with a putative nucleus-encoded DHBV:ferredoxin oxidoreductase (GtPEBA). A PEB:ferredoxin oxidoreductase (GtPEBB) was found to convert DHBV to PEB, which is the substrate for the phycobiliprotein lyase GtCPES. The x-ray structure of GtCPES was solved at 2.0 Å revealing a 10-stranded β-barrel with a modified lipocalin fold. GtCPES is an S-type lyase specific for binding of phycobilins with reduced C15=C16 double bonds (DHBV and PEB). Site-directed mutagenesis identified residues Glu-136 and Arg-146 involved in phycobilin binding. Based on the crystal structure, a model for the interaction of GtCPES with the apophycobiliprotein CpeB is proposed and discussed.
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Affiliation(s)
- Kristina E Overkamp
- Physiology of Microorganisms, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Raphael Gasper
- Protein Crystallography, Faculty for Biology and Biotechnology, and Ruhr University Bochum, 44780 Bochum, Germany
| | - Klaus Kock
- Physical Chemistry I, Protein Interactions, Faculty for Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
| | - Christian Herrmann
- Physical Chemistry I, Protein Interactions, Faculty for Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
| | - Eckhard Hofmann
- Protein Crystallography, Faculty for Biology and Biotechnology, and Ruhr University Bochum, 44780 Bochum, Germany
| | - Nicole Frankenberg-Dinkel
- Physiology of Microorganisms, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany.
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19
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Hanke G, Mulo P. Plant type ferredoxins and ferredoxin-dependent metabolism. PLANT, CELL & ENVIRONMENT 2013; 36:1071-1084. [PMID: 23190083 DOI: 10.1111/pce.12046] [Citation(s) in RCA: 176] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/19/2012] [Accepted: 11/20/2012] [Indexed: 05/24/2023]
Abstract
Ferredoxin (Fd) is a small [2Fe-2S] cluster-containing protein found in all organisms performing oxygenic photosynthesis. Fd is the first soluble acceptor of electrons on the stromal side of the chloroplast electron transport chain, and as such is pivotal to determining the distribution of these electrons to different metabolic reactions. In chloroplasts, the principle sink for electrons is in the production of NADPH, which is mostly consumed during the assimilation of CO2 . In addition to this primary function in photosynthesis, Fds are also involved in a number of other essential metabolic reactions, including biosynthesis of chlorophyll, phytochrome and fatty acids, several steps in the assimilation of sulphur and nitrogen, as well as redox signalling and maintenance of redox balance via the thioredoxin system and Halliwell-Asada cycle. This makes Fds crucial determinants of the electron transfer between the thylakoid membrane and a variety of soluble enzymes dependent on these electrons. In this article, we will first describe the current knowledge on the structure and function of the various Fd isoforms present in chloroplasts of higher plants and then discuss the processes involved in oxidation of Fd, introducing the corresponding enzymes and discussing what is known about their relative interaction with Fd.
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Affiliation(s)
- Guy Hanke
- Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrück, DE-49076, Osnabrück, Germany
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