1
|
Characterization of Molecular Diversity and Organization of Phycobilisomes in Thermophilic Cyanobacteria. Int J Mol Sci 2023; 24:ijms24065632. [PMID: 36982707 PMCID: PMC10053587 DOI: 10.3390/ijms24065632] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/07/2023] [Accepted: 03/14/2023] [Indexed: 03/18/2023] Open
Abstract
Thermophilic cyanobacteria are cosmopolitan and abundant in the thermal environment. Their light-harvesting complexes, phycobilisomes (PBS), are highly important in photosynthesis. To date, there is limited information on the PBS composition of thermophilic cyanobacteria whose habitats are challenging for survival. Herein, genome-based methods were used to investigate the molecular components of PBS in 19 well-described thermophilic cyanobacteria. These cyanobacteria are from the genera Leptolyngbya, Leptothermofonsia, Ocullathermofonsia, Thermoleptolyngbya, Trichothermofonsia, Synechococcus, Thermostichus, and Thermosynechococcus. According to the phycobiliprotein (PBP) composition of the rods, two pigment types are observed in these thermophiles. The amino acid sequence analysis of different PBP subunits suggests several highly conserved cysteine residues in these thermophiles. Certain amino acid contents in the PBP of thermophiles are significantly higher than their mesophilic counterparts, highlighting the potential roles of specific substitutions of amino acid in the adaptive thermostability of light-harvesting complexes in thermophilic cyanobacteria. Genes encoding PBS linker polypeptides vary among the thermophiles. Intriguingly, motifs in linker apcE indicate a photoacclimation of a far-red light by Leptolyngbya JSC-1, Leptothermofonsia E412, and Ocullathermofonsia A174. The composition pattern of phycobilin lyases is consistent among the thermophiles, except for Thermostichus strains that have extra homologs of cpcE, cpcF, and cpcT. In addition, phylogenetic analyses of genes coding for PBPs, linkers, and lyases suggest extensive genetic diversity among these thermophiles, which is further discussed with the domain analyses. Moreover, comparative genomic analysis suggests different genomic distributions of PBS-related genes among the thermophiles, indicating probably various regulations of expression. In summary, the comparative analysis elucidates distinct molecular components and organization of PBS in thermophilic cyanobacteria. These results provide insights into the PBS components of thermophilic cyanobacteria and fundamental knowledge for future research regarding structures, functions, and photosynthetic improvement.
Collapse
|
2
|
Carrigee LA, Frick JP, Liu X, Karty JA, Trinidad JC, Tom IP, Yang X, Dufour L, Partensky F, Schluchter WM. The phycoerythrobilin isomerization activity of MpeV in Synechococcus sp. WH8020 is prevented by the presence of a histidine at position 141 within its phycoerythrin-I β-subunit substrate. Front Microbiol 2022; 13:1011189. [PMID: 36458192 PMCID: PMC9705338 DOI: 10.3389/fmicb.2022.1011189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/12/2022] [Indexed: 11/17/2022] Open
Abstract
Marine Synechococcus efficiently harvest available light for photosynthesis using complex antenna systems, called phycobilisomes, composed of an allophycocyanin core surrounded by rods, which in the open ocean are always constituted of phycocyanin and two phycoerythrin (PE) types: PEI and PEII. These cyanobacteria display a wide pigment diversity primarily resulting from differences in the ratio of the two chromophores bound to PEs, the green-light absorbing phycoerythrobilin and the blue-light absorbing phycourobilin. Prior to phycobiliprotein assembly, bilin lyases post-translationally catalyze the ligation of phycoerythrobilin to conserved cysteine residues on α- or β-subunits, whereas the closely related lyase-isomerases isomerize phycoerythrobilin to phycourobilin during the attachment reaction. MpeV was recently shown in Synechococcus sp. RS9916 to be a lyase-isomerase which doubly links phycourobilin to two cysteine residues (C50 and C61; hereafter C50, 61) on the β-subunit of both PEI and PEII. Here we show that Synechococcus sp. WH8020, which belongs to the same pigment type as RS9916, contains MpeV that demonstrates lyase-isomerase activity on the PEII β-subunit but only lyase activity on the PEI β-subunit. We also demonstrate that occurrence of a histidine at position 141 of the PEI β-subunit from WH8020, instead of a leucine in its counterpart from RS9916, prevents the isomerization activity by WH8020 MpeV, showing for the first time that both the substrate and the enzyme play a role in the isomerization reaction. We propose a structural-based mechanism for the role of H141 in blocking isomerization. More generally, the knowledge of the amino acid present at position 141 of the β-subunits may be used to predict which phycobilin is bound at C50, 61 of both PEI and PEII from marine Synechococcus strains.
Collapse
Affiliation(s)
- Lyndsay A. Carrigee
- Department of Biological Sciences, University of New Orleans, New Orleans, LA, United States
- Environmental Laboratory, Engineering and Research Development Center, US Army Corps of Engineers, Vicksburg, MS, United States
| | - Jacob P. Frick
- Department of Biological Sciences, University of New Orleans, New Orleans, LA, United States
| | - Xindi Liu
- Department of Biological Sciences, University of New Orleans, New Orleans, LA, United States
| | - Jonathan A. Karty
- Department of Chemistry, Indiana University, Bloomington, IN, United States
| | | | - Irin P. Tom
- Department of Chemistry, University of Illinois Chicago, Chicago, IL, United States
| | - Xiaojing Yang
- Department of Chemistry, University of Illinois Chicago, Chicago, IL, United States
| | - Louison Dufour
- Ecology of Marine Plankton Team, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, Sorbonne Université, CNRS, Roscoff, France
| | - Frédéric Partensky
- Ecology of Marine Plankton Team, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, Sorbonne Université, CNRS, Roscoff, France
| | - Wendy M. Schluchter
- Department of Biological Sciences, University of New Orleans, New Orleans, LA, United States
- *Correspondence: Wendy M. Schluchter,
| |
Collapse
|
3
|
Derbel H, Elleuch J, Tounsi L, Nicolo MS, Rizzo MG, Michaud P, Fendri I, Abdelkafi S. Improvement of Biomass and Phycoerythrin Production by a Strain of Rhodomonas sp. Isolated from the Tunisian Coast of Sidi Mansour. Biomolecules 2022; 12:biom12070885. [PMID: 35883441 PMCID: PMC9312907 DOI: 10.3390/biom12070885] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/17/2022] [Accepted: 06/18/2022] [Indexed: 02/04/2023] Open
Abstract
Microalgae are photoautotrophic microorganisms known as producers of a large variety of metabolites. The taxonomic diversity of these microorganisms has been poorly explored. In this study, a newly isolated strain was identified based on the 18S rRNA encoding gene. The phylogenetic analysis showed that the isolated strain was affiliated with the Rhodomonas genus. This genus has greatly attracted scientific attention according to its capacity to produce a large variety of metabolites, including phycoerythrin. Growth and phycoerythrin production conditions were optimized using a Plackett–Burman design and response surface methodology. An expression profile analysis of the cpeB gene, encoding the beta subunit of phycoerythrin, was performed by qRT-PCR under standard and optimized culture conditions. The optimization process showed that maximum cell abundance was achieved under the following conditions: CaCl2 = 2.1328 g/L, metal solution = 1 mL/L, pH = 7 and light intensity = 145 μmol photons/m2/s, whereas maximum phycoerythrin production level occurred when CaCl2 = 1.8467 g/L, metal solution = 1 mL/L, pH = 7 and light intensity = 157 μmol/m2/s. In agreement, positive transcriptional regulation of the cpeB gene was demonstrated using qRT-PCR. This study showed the successful optimization of abiotic conditions for highest growth and phycoerythrin production, making Rhodomonas sp. suitable for several biotechnological applications.
Collapse
Affiliation(s)
- Hana Derbel
- Laboratoire de Génie Enzymatique et Microbiologie, Equipe de Biotechnologie des Algues, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, 3038 Sfax, Tunisia; (H.D.); (J.E.); (L.T.)
| | - Jihen Elleuch
- Laboratoire de Génie Enzymatique et Microbiologie, Equipe de Biotechnologie des Algues, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, 3038 Sfax, Tunisia; (H.D.); (J.E.); (L.T.)
| | - Latifa Tounsi
- Laboratoire de Génie Enzymatique et Microbiologie, Equipe de Biotechnologie des Algues, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, 3038 Sfax, Tunisia; (H.D.); (J.E.); (L.T.)
| | - Marco Sebastiano Nicolo
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale F. Stagno d’Alcontres, 31, 98166 Messina, Italy; (M.S.N.); (M.G.R.)
| | - Maria Giovanna Rizzo
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale F. Stagno d’Alcontres, 31, 98166 Messina, Italy; (M.S.N.); (M.G.R.)
| | - Philippe Michaud
- Institut Pascal, Université Clermont Auvergne, CNRS, Clermont Auvergne INP, 63178 Clermont-Ferrand, France
- Correspondence: (P.M.); (S.A.); Tel.: +33-475407425 (P.M.); +216-97-458-923 (S.A.)
| | - Imen Fendri
- Laboratory of Plant Biotechnology, Faculty of Sciences of Sfax, University of Sfax, 3038 Sfax, Tunisia;
| | - Slim Abdelkafi
- Laboratoire de Génie Enzymatique et Microbiologie, Equipe de Biotechnologie des Algues, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, 3038 Sfax, Tunisia; (H.D.); (J.E.); (L.T.)
- Correspondence: (P.M.); (S.A.); Tel.: +33-475407425 (P.M.); +216-97-458-923 (S.A.)
| |
Collapse
|
4
|
Grébert T, Garczarek L, Daubin V, Humily F, Marie D, Ratin M, Devailly A, Farrant GK, Mary I, Mella-Flores D, Tanguy G, Labadie K, Wincker P, Kehoe DM, Partensky F. Diversity and evolution of pigment types in marine Synechococcus cyanobacteria. Genome Biol Evol 2022; 14:6547267. [PMID: 35276007 PMCID: PMC8995045 DOI: 10.1093/gbe/evac035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2022] [Indexed: 11/14/2022] Open
Abstract
Synechococcus cyanobacteria are ubiquitous and abundant in the marine environment and contribute to an estimated 16% of the ocean net primary productivity. Their light-harvesting complexes, called phycobilisomes (PBS), are composed of a conserved allophycocyanin core, from which radiates six to eight rods with variable phycobiliprotein and chromophore content. This variability allows Synechococcus cells to optimally exploit the wide variety of spectral niches existing in marine ecosystems. Seven distinct pigment types or subtypes have been identified so far in this taxon based on the phycobiliprotein composition and/or the proportion of the different chromophores in PBS rods. Most genes involved in their biosynthesis and regulation are located in a dedicated genomic region called the PBS rod region. Here, we examine the variability of gene content and organization of this genomic region in a large set of sequenced isolates and natural populations of Synechococcus representative of all known pigment types. All regions start with a tRNA-PheGAA and some possess mobile elements for DNA integration and site-specific recombination, suggesting that their genomic variability relies in part on a “tycheposon”-like mechanism. Comparison of the phylogenies obtained for PBS and core genes revealed that the evolutionary history of PBS rod genes differs from the core genome and is characterized by the co-existence of different alleles and frequent allelic exchange. We propose a scenario for the evolution of the different pigment types and highlight the importance of incomplete lineage sorting in maintaining a wide diversity of pigment types in different Synechococcus lineages despite multiple speciation events.
Collapse
Affiliation(s)
- Théophile Grébert
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Laurence Garczarek
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Vincent Daubin
- Université Lyon 1, UMR 5558 Biometry and Evolutionary Biology, 69622 Villeurbanne, France
| | - Florian Humily
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Dominique Marie
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Morgane Ratin
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Alban Devailly
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Gregory K Farrant
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Isabelle Mary
- Université Clermont Auvergne, CNRS, Laboratoire Microorganismes: Génome et Environnement, 63000 Clermont-Ferrand, France
| | - Daniella Mella-Flores
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| | - Gwenn Tanguy
- Centre National de la Recherche Scientifique, FR 2424, Station Biologique, 29680 Roscoff, France
| | - Karine Labadie
- Genoscope, Institut de biologie François-Jacob, Commissariat à l'Énergie Atomique (CEA), Université Paris-Saclay, Evry, France
| | - Patrick Wincker
- Génomique Métabolique, Genoscope, Institut de biologie François Jacob, CEA, CNRS, Université d'Evry, Université Paris-Saclay, Evry, France
| | - David M Kehoe
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Frédéric Partensky
- Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7144 Adaptation and Diversity in the Marine Environment, Station Biologique, 29680 Roscoff, France
| |
Collapse
|
5
|
Kumarapperuma I, Joseph KL, Wang C, Biju LM, Tom IP, Weaver KD, Grébert T, Partensky F, Schluchter WM, Yang X. Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase. Structure 2022; 30:564-574.e3. [PMID: 35148828 PMCID: PMC8995348 DOI: 10.1016/j.str.2022.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 12/01/2021] [Accepted: 01/17/2022] [Indexed: 12/19/2022]
Abstract
Chromophore attachment of the light-harvesting apparatus represents one of the most important post-translational modifications in photosynthetic cyanobacteria. Extensive pigment diversity of cyanobacteria critically depends on bilin lyases that covalently attach chemically distinct chromophores to phycobiliproteins. However, how bilin lyases catalyze bilin ligation reactions and how some lyases acquire additional isomerase abilities remain elusive at the molecular level. Here, we report the crystal structure of a representative bilin lyase-isomerase MpeQ. This structure has revealed a "question-mark" protein architecture that unambiguously establishes the active site conserved among the E/F-type bilin lyases. Based on structural, mutational, and modeling data, we demonstrate that stereoselectivity of the active site plays a critical role in conferring the isomerase activity of MpeQ. We further advance a tyrosine-mediated reaction scheme unifying different types of bilin lyases. These results suggest that lyases and isomerase actions of bilin lyases arise from two coupled molecular events of distinct origin.
Collapse
|
6
|
Carrigee LA, Frick JP, Karty JA, Garczarek L, Partensky F, Schluchter WM. MpeV is a lyase isomerase that ligates a doubly linked phycourobilin on the β-subunit of phycoerythrin I and II in marine Synechococcus. J Biol Chem 2021; 296:100031. [PMID: 33154169 PMCID: PMC7948978 DOI: 10.1074/jbc.ra120.015289] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 11/04/2020] [Accepted: 11/05/2020] [Indexed: 11/06/2022] Open
Abstract
Synechococcus cyanobacteria are widespread in the marine environment, as the extensive pigment diversity within their light-harvesting phycobilisomes enables them to utilize various wavelengths of light for photosynthesis. The phycobilisomes of Synechococcus sp. RS9916 contain two forms of the protein phycoerythrin (PEI and PEII), each binding two chromophores, green-light absorbing phycoerythrobilin and blue-light absorbing phycourobilin. These chromophores are ligated to specific cysteines via bilin lyases, and some of these enzymes, called lyase isomerases, attach phycoerythrobilin and simultaneously isomerize it to phycourobilin. MpeV is a putative lyase isomerase whose role in PEI and PEII biosynthesis is not clear. We examined MpeV in RS9916 using recombinant protein expression, absorbance spectroscopy, and tandem mass spectrometry. Our results show that MpeV is the lyase isomerase that covalently attaches a doubly linked phycourobilin to two cysteine residues (C50, C61) on the β-subunit of both PEI (CpeB) and PEII (MpeB). MpeV activity requires that CpeB or MpeB is first chromophorylated by the lyase CpeS (which adds phycoerythrobilin to C82). Its activity is further enhanced by CpeZ (a homolog of a chaperone-like protein first characterized in Fremyella diplosiphon). MpeV showed no detectable activity on the α-subunits of PEI or PEII. The mechanism by which MpeV links the A and D rings of phycourobilin to C50 and C61 of CpeB was also explored using site-directed mutants, revealing that linkage at the A ring to C50 is a critical step in chromophore attachment, isomerization, and stability. These data provide novel insights into β-PE biosynthesis and advance our understanding of the mechanisms guiding lyase isomerases.
Collapse
Affiliation(s)
- Lyndsay A Carrigee
- Department of Biological Sciences, University of New Orleans, New Orleans, Louisiana, USA
| | - Jacob P Frick
- Department of Biological Sciences, University of New Orleans, New Orleans, Louisiana, USA
| | - Jonathan A Karty
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Laurence Garczarek
- Ecology of Marine Plankton (ECOMAP) Team, Station Biologique, Sorbonne Université & CNRS, UMR 7144, Roscoff, France
| | - Frédéric Partensky
- Ecology of Marine Plankton (ECOMAP) Team, Station Biologique, Sorbonne Université & CNRS, UMR 7144, Roscoff, France
| | - Wendy M Schluchter
- Department of Biological Sciences, University of New Orleans, New Orleans, Louisiana, USA.
| |
Collapse
|
7
|
Nguyen AA, Joseph KL, Bussell AN, Pokhrel S, Karty JA, Kronfel CM, Kehoe DM, Schluchter WM. CpeT is the phycoerythrobilin lyase for Cys-165 on β-phycoerythrin from Fremyella diplosiphon and the chaperone-like protein CpeZ greatly improves its activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148284. [PMID: 32777305 DOI: 10.1016/j.bbabio.2020.148284] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/31/2020] [Accepted: 08/04/2020] [Indexed: 10/23/2022]
Abstract
Bilin lyases are enzymes which ligate linear tetrapyrrole chromophores to specific cysteine residues on light harvesting proteins present in cyanobacteria and red algae. The lyases responsible for chromophorylating the light harvesting protein phycoerythrin (PE) have not been fully characterized. In this study, we explore the role of CpeT, a putative bilin lyase, in the biosynthesis of PE in the cyanobacterium Fremyella diplosiphon. Recombinant protein studies show that CpeT alone can bind phycoerythrobilin (PEB), but CpeZ, a chaperone-like protein, is needed in order to correctly and efficiently attach PEB to the β-subunit of PE. MS analyses of the recombinant β-subunit of PE coexpressed with CpeT and CpeZ show that PEB is attached at Cys-165. Purified phycobilisomes from a cpeT knockout mutant and wild type (WT) samples from F. diplosiphon were analyzed and compared. The cpeT mutant contained much less PE and more phycocyanin than WT cells grown under green light, conditions which should maximize the production of PE. In addition, Northern blot analyses showed that the cpeCDESTR operon mRNAs were upregulated while the cpeBcpeA mRNAs were downregulated in the cpeT mutant strain when compared with WT, suggesting that CpeT may also play a direct or indirect regulatory role in transcription of these operons or their mRNA stability, in addition to its role as a PEB lyase for Cys-165 on β-PE.
Collapse
Affiliation(s)
- Adam A Nguyen
- Department of Chemistry, University of New Orleans, New Orleans, LA 70148, USA; Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Kes Lynn Joseph
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Adam N Bussell
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Suman Pokhrel
- Department of Chemistry, University of New Orleans, New Orleans, LA 70148, USA; Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Jonathan A Karty
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Christina M Kronfel
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - David M Kehoe
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Wendy M Schluchter
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA.
| |
Collapse
|
8
|
Carrigee LA, Mahmoud RM, Sanfilippo JE, Frick JP, Strnat JA, Karty JA, Chen B, Kehoe DM, Schluchter WM. CpeY is a phycoerythrobilin lyase for cysteine 82 of the phycoerythrin I α-subunit in marine Synechococcus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148215. [PMID: 32360311 DOI: 10.1016/j.bbabio.2020.148215] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 04/24/2020] [Accepted: 04/27/2020] [Indexed: 11/15/2022]
Abstract
Marine Synechococcus are widespread in part because they are efficient at harvesting available light using their complex antenna, or phycobilisome, composed of multiple phycobiliproteins and bilin chromophores. Over 40% of Synechococcus strains are predicted to perform a type of chromatic acclimation that alters the ratio of two chromophores, green-light-absorbing phycoerythrobilin and blue-light-absorbing phycourobilin, to optimize light capture by phycoerythrin in the phycobilisome. Lyases are enzymes which catalyze the addition of bilin chromophores to specific cysteine residues on phycobiliproteins and are involved in chromatic acclimation. CpeY, a candidate lyase in the model strain Synechococcus sp. RS9916, added phycoerythrobilin to cysteine 82 of only the α subunit of phycoerythrin I (CpeA) in the presence or absence of the chaperone-like protein CpeZ in a recombinant protein expression system. These studies demonstrated that recombinant CpeY attaches phycoerythrobilin to as much as 72% of CpeA, making it one of the most efficient phycoerythrin lyases characterized to date. Phycobilisomes from a cpeY- mutant showed a near native bilin composition in all light conditions except for a slight replacement of phycoerythrobilin by phycourobilin at CpeA cysteine 82. This demonstrates that CpeY is not involved in any chromatic acclimation-driven chromophore changes and suggests that the chromophore attached at cysteine 82 of CpeA in the cpeY- mutant is ligated by an alternative phycoerythrobilin lyase. Although loss of CpeY does not greatly inhibit native phycobilisome assembly in vivo, the highly active recombinant CpeY can be used to generate large amounts of fluorescent CpeA for biotechnological uses.
Collapse
Affiliation(s)
- Lyndsay A Carrigee
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Rania M Mahmoud
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Department of Botany, Faculty of Science, University of Fayoum, Fayoum, Egypt
| | | | - Jacob P Frick
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Johann A Strnat
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Jonathan A Karty
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Bo Chen
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - David M Kehoe
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Wendy M Schluchter
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA.
| |
Collapse
|