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1.
Int J Mol Sci ; 22(6)2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33804002

RESUMO

Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.


Assuntos
Proteína do Homeodomínio de Antennapedia/genética , Complexos de Proteínas Captadores de Luz/genética , Processos Fototróficos/genética , Agregados Proteicos/genética , Proteína do Homeodomínio de Antennapedia/química , Clorofila/química , Clorofila/genética , Clorofila/efeitos da radiação , Análise por Conglomerados , Fluorescência , Concentração de Íons de Hidrogênio , Luz/efeitos adversos , Complexos de Proteínas Captadores de Luz/química , Fotossíntese/genética , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/efeitos da radiação , Espectrometria de Fluorescência , Tilacoides/química , Tilacoides/genética , Tilacoides/efeitos da radiação , Zeaxantinas/genética
2.
Nat Commun ; 12(1): 1104, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33597527

RESUMO

Photosynthetic electron transfers occur through multiple components ranging from small soluble proteins to large integral membrane protein complexes. Co-crystallization of a bacterial photosynthetic electron transfer complex that employs weak hydrophobic interactions was achieved by using high-molar-ratio mixtures of a soluble donor protein (high-potential iron-sulfur protein, HiPIP) with a membrane-embedded acceptor protein (reaction center, RC) at acidic pH. The structure of the co-complex offers a snapshot of a transient bioenergetic event and revealed a molecular basis for thermodynamically unfavorable interprotein electron tunneling. HiPIP binds to the surface of the tetraheme cytochrome subunit in the light-harvesting (LH1) complex-associated RC in close proximity to the low-potential heme-1 group. The binding interface between the two proteins is primarily formed by uncharged residues and is characterized by hydrophobic features. This co-crystal structure provides a model for the detailed study of long-range trans-protein electron tunneling pathways in biological systems.


Assuntos
Proteínas de Bactérias/química , Chromatiaceae/metabolismo , Proteínas com Ferro-Enxofre/química , Complexos de Proteínas Captadores de Luz/química , Fotossíntese , Complexo de Proteínas do Centro de Reação Fotossintética/química , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Cristalização , Citocromos/química , Citocromos/metabolismo , Transporte de Elétrons , Heme/análogos & derivados , Heme/química , Heme/metabolismo , Proteínas com Ferro-Enxofre/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Moleculares , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Conformação Proteica , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
3.
Nat Commun ; 12(1): 1100, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33597543

RESUMO

Photosystem I (PSI) and II (PSII) balance their light energy distribution absorbed by their light-harvesting complexes (LHCs) through state transition to maintain the maximum photosynthetic performance and to avoid photodamage. In state 2, a part of LHCII moves to PSI, forming a PSI-LHCI-LHCII supercomplex. The green alga Chlamydomonas reinhardtii exhibits state transition to a far larger extent than higher plants. Here we report the cryo-electron microscopy structure of a PSI-LHCI-LHCII supercomplex in state 2 from C. reinhardtii at 3.42 Å resolution. The result reveals that the PSI-LHCI-LHCII of C. reinhardtii binds two LHCII trimers in addition to ten LHCI subunits. The PSI core subunits PsaO and PsaH, which were missed or not well-resolved in previous Cr-PSI-LHCI structures, are observed. The present results reveal the organization and assembly of PSI core subunits, LHCI and LHCII, pigment arrangement, and possible pathways of energy transfer from peripheral antennae to the PSI core.


Assuntos
Proteínas de Algas/metabolismo , Chlamydomonas reinhardtii/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Proteínas de Algas/química , Proteínas de Algas/ultraestrutura , Clorofila/metabolismo , Microscopia Crioeletrônica , Transferência de Energia , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/ultraestrutura , Modelos Moleculares , Fotossíntese , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/ultraestrutura , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/metabolismo , Complexo de Proteína do Fotossistema II/ultraestrutura , Ligação Proteica , Conformação Proteica , Multimerização Proteica , Tilacoides/metabolismo , Tilacoides/ultraestrutura
4.
BMC Plant Biol ; 21(1): 106, 2021 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-33610179

RESUMO

BACKGROUND: Photosystem II (PSII) is a highly conserved integral-membrane multi-subunit pigment-protein complex. The proteins, pigments, lipids, and ions in PSII need to be assembled precisely to ensure a proper PSII biogenesis. D1 is the main subunit of PSII core reaction center (RC), and is usually synthesized as a precursor D1. D1 maturation by the C-terminal processing protease CtpA is essential for PSII assembly. However, the detailed mechanism about how D1 maturation affects PSII assembly is not clearly elucidated so far. In this study, Arabidopsis thaliana CtpA mutant (atctpa: SALK_056011), which lacks the D1 mature process, was used to investigate the function of this process on PSII assembly in more details. RESULTS: Without the C-terminal processing of precursor D1, PSII assembly, including PSII monomer, dimer, especially PSII supercomplexes (PSII SCs), was largely compromised as reported previously. Western blotting following the BN-2D-SDS PAGE revealed that although the assembly of PSII core proteins D2, CP43 and CP47 was affected by the loss of D1 mature process, the incorporation of CP43 was affected the most, indicated by its most reduced assembly efficiency into PSII SCs. Furthermore, the slower growth of yeast cells which were co-transformed with pD1 and CP43, when compared with the ones co-transformed with mature D1 and CP43, approved the existence of D1 C-terminal tail hindered the interaction efficiency between D1 and CP43, indicating the physiological importance of D1 mature process on the PSII assembly and the healthy growth of the organisms. CONCLUSIONS: The knockout Arabidopsis atctpa mutant is a good material to study the unexpected link between D1 maturation and PSII SCs assembly. The loss of D1 maturation mainly affects the incorporation of PSII core protein CP43, an inner antenna binding protein, which functions in the association of LHCII complexes to PSII dimers during the formation of PSII SCs. Our findings here provide detailed supports of the role of D1 maturation during PSII SCs assembly in higher plants.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Peptídeo Hidrolases/metabolismo , Fotossíntese/genética , Fotossíntese/fisiologia , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Peptídeo Hidrolases/genética
5.
Phys Chem Chem Phys ; 23(2): 806-821, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33427836

RESUMO

Diatoms are a major group of algae, responsible for a quarter of the global primary production on our planet. Their adaptation to marine environments is ensured by their light-harvesting antenna - the fucoxanthin-chlorophyll protein (FCP) complex, which absorbs strongly in the blue-green spectral region. Although these essential proteins have been the subject of many studies, for a long time their comprehensive description was not possible in the absence of structural data. Last year, the 3D structures of several FCP complexes were revealed. The structure of an FCP dimer was resolved by crystallography for the pennate diatom Phaeodactylum tricornutum [W. Wang et al., Science, 2019, 363, 6427] and the structure of the PSII supercomplex from the centric diatom Chaetoceros gracilis, containing several FCPs, was obtained by electron microscopy [X. Pi et al., Science, 2019, 365, 6452; R. Nagao et al., Nat. Plants, 2019, 5, 890]. In this Perspective article, we evaluate how precisely these structures may account for previously published ultrafast spectroscopy results, describing the excitation energy transfer in the FCP from another centric diatom Cyclotella meneghiniana. Surprisingly, we find that the published FCP structures cannot explain several observations obtained from ultrafast spectroscopy. Using the available structures, and results from electron microscopy, we construct a trimer-based FCP model for Cyclotella meneghiniana, consistent with ultrafast experimental data. As a whole, our observations suggest that the structures from the proteins belonging to the FCP family display larger variations than the equivalent LHC proteins in plants, which may reflect species-specific adaptations or original strategies for adapting to rapidly changing marine environments.


Assuntos
Clorofila A/química , Complexos de Proteínas Captadores de Luz/química , Xantofilas/química , Sequência de Aminoácidos , Clorofila/química , Diatomáceas/química , Transferência de Energia , Conformação Proteica , Espectrometria de Fluorescência
6.
Biochim Biophys Acta Bioenerg ; 1862(1): 148307, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-32926863

RESUMO

Redox-active quinones play essential roles in efficient light energy conversion in type-II reaction centers of purple phototrophic bacteria. In the light-harvesting 1 reaction center (LH1-RC) complex of purple bacteria, QB is converted to QBH2 upon light-induced reduction and QBH2 is transported to the quinone pool in the membrane through the LH1 ring. In the purple bacterium Rhodobacter sphaeroides, the C-shaped LH1 ring contains a gap for quinone transport. In contrast, the thermophilic purple bacterium Thermochromatium (Tch.) tepidum has a closed O-shaped LH1 ring that lacks a gap, and hence the mechanism of photosynthetic quinone transport is unclear. Here we detected light-induced Fourier transform infrared (FTIR) signals responsible for changes of QB and its binding site that accompany photosynthetic quinone reduction in Tch. tepidum and characterized QB and QBH2 marker bands based on their 15N- and 13C-isotopic shifts. Quinone exchanges were monitored using reconstituted photosynthetic membranes comprised of solubilized photosynthetic proteins, membrane lipids, and exogenous ubiquinone (UQ) molecules. In combination with 13C-labeling of the LH1-RC and replacement of native UQ8 by ubiquinones of different tail lengths, we demonstrated that quinone exchanges occur efficiently within the hydrophobic environment of the lipid membrane and depend on the side chain length of UQ. These results strongly indicate that unlike the process in Rba. sphaeroides, quinone transport in Tch. tepidum occurs through the size-restricted hydrophobic channels in the closed LH1 ring and are consistent with structural studies that have revealed narrow hydrophobic channels in the Tch. tepidum LH1 transmembrane region.


Assuntos
Proteínas de Bactérias/química , Chromatiaceae/enzimologia , Complexos de Proteínas Captadores de Luz/química , Ubiquinona/química , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Transporte Biológico Ativo , Complexos de Proteínas Captadores de Luz/metabolismo , Oxirredução , Ubiquinona/metabolismo
7.
Biochim Biophys Acta Bioenerg ; 1862(1): 148327, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33069682

RESUMO

Iron-stress-induced-A proteins (IsiAs) are expressed in cyanobacteria under iron-deficient conditions, and surround photosystem I (PSI) trimer with a ring formation. A cyanobacterium Anabaena sp. PCC 7120 has four isiA genes; however, it is unknown how the IsiAs are associated with PSI. Here we report on molecular organizations and function of the IsiAs in this cyanobacterium. A deletion mutant of the isiA1 gene was constructed, and the four types of thylakoids were prepared from the wild-type (WT) and ΔisiA1 cells under iron-replete (+Fe) and iron-deficient (-Fe) conditions. Immunoblotting analysis exhibits a clear expression of the IsiA1 in the WT-Fe. The PSI-IsiA1 supercomplex is found in the WT-Fe, and excitation-energy transfer from IsiA1 to PSI is verified by time-resolved fluorescence analyses. Instead of the IsiA1, both IsiA2 and IsiA3 are bound to PSI monomer in the ΔisiA1-Fe. These findings provide insights into multiple-expression system of the IsiA family in this cyanobacterium.


Assuntos
Anabaena/enzimologia , Proteínas de Bactérias/metabolismo , Ferro/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Família Multigênica , Anabaena/genética , Proteínas de Bactérias/genética , Deleção de Genes , Regulação Bacteriana da Expressão Gênica , Complexos de Proteínas Captadores de Luz/genética
8.
Nat Commun ; 11(1): 4955, 2020 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-33009385

RESUMO

The light-harvesting-reaction center complex (LH1-RC) from the purple phototrophic bacterium Thiorhodovibrio strain 970 exhibits an LH1 absorption maximum at 960 nm, the most red-shifted absorption for any bacteriochlorophyll (BChl) a-containing species. Here we present a cryo-EM structure of the strain 970 LH1-RC complex at 2.82 Å resolution. The LH1 forms a closed ring structure composed of sixteen pairs of the αß-polypeptides. Sixteen Ca ions are present in the LH1 C-terminal domain and are coordinated by residues from the αß-polypeptides that are hydrogen-bonded to BChl a. The Ca2+-facilitated hydrogen-bonding network forms the structural basis of the unusual LH1 redshift. The structure also revealed the arrangement of multiple forms of α- and ß-polypeptides in an individual LH1 ring. Such organization indicates a mechanism of interplay between the expression and assembly of the LH1 complex that is regulated through interactions with the RC subunits inside.


Assuntos
Cálcio/metabolismo , Microscopia Crioeletrônica , Complexos de Proteínas Captadores de Luz/ultraestrutura , Peptídeos/metabolismo , Fotossíntese , Sequência de Aminoácidos , Bacterioclorofila A/metabolismo , Sítios de Ligação , Chromatiaceae/metabolismo , Detergentes/química , Dimerização , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/metabolismo , Lipídeos/química , Peptídeos/química , Quinonas/química
9.
Nat Commun ; 11(1): 5081, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033236

RESUMO

Diatom is an important group of marine algae and contributes to around 20% of the global photosynthetic carbon fixation. Photosystem I (PSI) of diatoms is associated with a large number of fucoxanthin-chlorophyll a/c proteins (FCPIs). We report the structure of PSI-FCPI from a diatom Chaetoceros gracilis at 2.38 Å resolution by single-particle cryo-electron microscopy. PSI-FCPI is a monomeric supercomplex consisting of 12 core and 24 antenna subunits (FCPIs), and 326 chlorophylls a, 34 chlorophylls c, 102 fucoxanthins, 35 diadinoxanthins, 18 ß-carotenes and some electron transfer cofactors. Two subunits designated PsaR and PsaS were found in the core, whereas several subunits were lost. The large number of pigments constitute a unique and huge network ensuring efficient energy harvesting, transfer and dissipation. These results provide a firm structural basis for unraveling the mechanisms of light-energy harvesting, transfer and quenching in the diatom PSI-FCPI, and also important clues to evolutionary changes of PSI-LHCI.


Assuntos
Proteínas de Ligação à Clorofila/química , Diatomáceas/metabolismo , Transferência de Energia , Complexo de Proteína do Fotossistema I/química , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/metabolismo , Pigmentos Biológicos/química , Pigmentos Biológicos/metabolismo , Subunidades Proteicas/química
10.
Proc Natl Acad Sci U S A ; 117(30): 17499-17509, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32690715

RESUMO

Coping of evergreen conifers in boreal forests with freezing temperatures on bright winter days puts the photosynthetic machinery in great risk of oxidative damage. To survive harsh winter conditions, conifers have evolved a unique but poorly characterized photoprotection mechanism, a sustained form of nonphotochemical quenching (sustained NPQ). Here we focused on functional properties and underlying molecular mechanisms related to the development of sustained NPQ in Norway spruce (Picea abies). Data were collected during 4 consecutive years (2016 to 2019) from trees growing in sun and shade habitats. When day temperatures dropped below -4 °C, the specific N-terminally triply phosphorylated LHCB1 isoform (3p-LHCII) and phosphorylated PSBS (p-PSBS) could be detected in the thylakoid membrane. Development of sustained NPQ coincided with the highest level of 3p-LHCII and p-PSBS, occurring after prolonged coincidence of bright winter days and temperatures close to -10 °C. Artificial induction of both the sustained NPQ and recovery from naturally induced sustained NPQ provided information on differential dynamics and light-dependence of 3p-LHCII and p-PSBS accumulation as prerequisites for sustained NPQ. Data obtained collectively suggest three components related to sustained NPQ in spruce: 1) Freezing temperatures induce 3p-LHCII accumulation independently of light, which is suggested to initiate destacking of appressed thylakoid membranes due to increased electrostatic repulsion of adjacent membranes; 2) p-PSBS accumulation is both light- and temperature-dependent and closely linked to the initiation of sustained NPQ, which 3) in concert with PSII photoinhibition, is suggested to trigger sustained NPQ in spruce.


Assuntos
Fotossíntese , Picea/fisiologia , Estações do Ano , Proteínas das Membranas dos Tilacoides/metabolismo , Tilacoides/metabolismo , Sequência de Aminoácidos , Meio Ambiente , Complexos de Proteínas Captadores de Luz/metabolismo , Noruega , Fosforilação , Espectrometria de Massas em Tandem , Proteínas das Membranas dos Tilacoides/química , Árvores
11.
Science ; 368(6498): 1427-1428, 2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32587007
12.
Science ; 368(6498): 1490-1495, 2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32587021

RESUMO

Photosynthesis achieves near unity light-harvesting quantum efficiency yet it remains unknown whether there exists a fundamental organizing principle giving rise to robust light harvesting in the presence of dynamic light conditions and noisy physiological environments. Here, we present a noise-canceling network model that relates noisy physiological conditions, power conversion efficiency, and the resulting absorption spectra of photosynthetic organisms. Using light conditions in full solar exposure, light filtered by oxygenic phototrophs, and light filtered under seawater, we derived optimal absorption characteristics for efficient solar power conversion. We show how light-harvesting antennae can be tuned to maximize power conversion efficiency by minimizing excitation noise, thus providing a unified theoretical basis for the observed wavelength dependence of absorption in green plants, purple bacteria, and green sulfur bacteria.


Assuntos
Complexos de Proteínas Captadores de Luz/fisiologia , Fotossíntese , Plantas/metabolismo , Proteobactérias/metabolismo , Adsorção , Chlorobi , Transferência de Energia , Luz , Oxigênio , Energia Solar
13.
Nat Commun ; 11(1): 2481, 2020 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-32424145

RESUMO

Photosynthetic light-harvesting complexes (LHCs) play a pivotal role in collecting solar energy for photochemical reactions in photosynthesis. One of the major LHCs are fucoxanthin chlorophyll a/c-binding proteins (FCPs) present in diatoms, a group of organisms having important contribution to the global carbon cycle. Here, we report a 2.40-Å resolution structure of the diatom photosystem I (PSI)-FCPI supercomplex by cryo-electron microscopy. The supercomplex is composed of 16 different FCPI subunits surrounding a monomeric PSI core. Each FCPI subunit showed different protein structures with different pigment contents and binding sites, and they form a complicated pigment-protein network together with the PSI core to harvest and transfer the light energy efficiently. In addition, two unique, previously unidentified subunits were found in the PSI core. The structure provides numerous insights into not only the light-harvesting strategy in diatom PSI-FCPI but also evolutionary dynamics of light harvesters among oxyphototrophs.


Assuntos
Diatomáceas/metabolismo , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/metabolismo , Clorofila/metabolismo , Proteínas de Ligação à Clorofila/química , Proteínas de Ligação à Clorofila/ultraestrutura , Transferência de Energia , Complexos de Proteínas Captadores de Luz/ultraestrutura , Modelos Moleculares , Complexo de Proteína do Fotossistema I/ultraestrutura , Ligação Proteica , Subunidades Proteicas/metabolismo , Relação Estrutura-Atividade
14.
J Phys Chem Lett ; 11(9): 3242-3248, 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32271019

RESUMO

Photosystem II (PSII) converts light into chemical energy powering almost all life on Earth. The primary photovoltaic reaction in the PSII reaction center requires energy corresponding to 680 nm, which is significantly higher than in the case of the low-energy states in the antenna complexes involved in the harvesting of excitations driving PSII. Here we show that despite seemingly insufficient energy, the low-energy excited states can power PSII because of the activity of the thermally driven up-conversion. We demonstrate the operation of this mechanism both in intact leaves and in isolated pigment-protein complex LHCII. A mechanism is proposed, according to which the effective utilization of thermal energy in the photosynthetic apparatus is possible owing to the formation of LHCII supramolecular structures, leading to the coupled energy levels corresponding to approximately 680 and 700 nm, capable of exchanging excitation energy through the spontaneous relaxation and the thermal up-conversion.


Assuntos
Transferência de Energia , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Arabidopsis/metabolismo , Clorofila A/metabolismo , Temperatura Alta , Folhas de Planta/metabolismo , Reciclagem , Espectrometria de Fluorescência
15.
Biochim Biophys Acta Bioenerg ; 1861(8): 148205, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32305413

RESUMO

An increased robustness against high temperature and the much red-shifted near-infrared absorption spectrum of excitons in the LH1-RC core pigment-protein complex from the thermophilic photosynthetic purple sulfur bacterium Thermochromatium tepidum has recently attracted much interest. In the present work, thermal and hydrostatic pressure stability of the peripheral LH2 and core LH1-RC complexes from this bacterium were in parallel investigated by various optical spectroscopy techniques applied over a wide spectral range from far-ultraviolet to near-infrared. In contrast to expectations, very distinct robustness of the complexes was established, while the sturdiness of LH2 surpassed that of LH1-RC both with respect to temperatures between 288 and 360 K, and pressures between 1 bar and 14 kbar. Subtle structural variances related to the hydrogen bond network are likely responsible for the extra stability of LH2.


Assuntos
Chromatiaceae/enzimologia , Complexos de Proteínas Captadores de Luz/metabolismo , Pressão , Temperatura , Elétrons , Complexos de Proteínas Captadores de Luz/química , Prótons
16.
Appl Environ Microbiol ; 86(13)2020 06 17.
Artigo em Inglês | MEDLINE | ID: mdl-32332138

RESUMO

Microorganisms in nature are commonly exposed to various stresses in parallel. The isiA gene encodes an iron stress-induced chlorophyll-binding protein which is significantly induced under iron starvation and oxidative stress. Acclimation of oxidative stress and iron deficiency was investigated using a regulatory mutant of the Synechocystis sp. strain PCC 6803. In this study, the ΔisiA mutant grew more slowly in oxidative-stress and iron depletion conditions compared to the wild-type (WT) counterpart under the same conditions. Thus, we performed transcriptome sequencing (RNA-seq) analysis of the WT strain and the ΔisiA mutant under double-stress conditions to obtain a comprehensive view of isiA-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed significant differences between the WT strain and ΔisiA mutant, mainly related to photosynthesis and the iron-sulfur cluster. The deletion of isiA affects the expression of various genes that are involved in cellular processes and structures, such as photosynthesis, phycobilisome, and the proton-transporting ATPase complex. Weighted gene coexpression network analysis (WGCNA) demonstrated three functional modules in which the turquoise module was negatively correlated with superoxide dismutase (SOD) activity. Coexpression network analysis identified several hub genes of each module. Cotranscriptional PCR and reads coverage using the Integrative Genomics Viewer demonstrated that isiA, isiB, isiC, ssl0461, and dfp belonged to the isi operon. Three sRNAs related to oxidative stress were identified. This study enriches our knowledge of IsiA-regulatory mechanisms under iron deficiency and oxidative stress.IMPORTANCE This study analyzed the impact of isiA deletion on the transcriptomic profile of Synechocystis The isiA gene encodes an iron stress-induced chlorophyll-binding protein, which is significantly induced under iron starvation. The deletion of isiA affects the expression of various genes that are involved in photosynthesis and ABC transporters. WGCNA revealed three functional modules in which the blue module was correlated with oxidative stress. We further demonstrated that the isi operon contained the following five genes: isiA, isiB, isiC, ssl0461, and dfp by cotranscriptional PCR. Three sRNAs were identified that were related to oxidative stress. This study enhances our knowledge of IsiA-regulatory mechanisms under iron deficiency and oxidative stress.


Assuntos
Proteínas de Bactérias/genética , Ferro/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Estresse Oxidativo , Synechocystis/fisiologia , Aclimatação , Proteínas de Bactérias/metabolismo , Perfilação da Expressão Gênica , Complexos de Proteínas Captadores de Luz/metabolismo , Synechocystis/genética
17.
Int J Mol Sci ; 21(7)2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32244795

RESUMO

The effects of combining naturally evolved photosynthetic pigment-protein complexes with inorganic functional materials, especially plasmonically active metallic nanostructures, have been a widely studied topic in the last few decades. Besides other applications, it seems to be reasonable using such hybrid systems for designing future biomimetic solar cells. In this paper, we describe selected results that point out to various aspects of the interactions between photosynthetic complexes and plasmonic excitations in Silver Island Films (SIFs). In addition to simple light-harvesting complexes, like peridinin-chlorophyll-protein (PCP) or the Fenna-Matthews-Olson (FMO) complex, we also discuss the properties of large, photosynthetic reaction centers (RCs) and Photosystem I (PSI)-both prokaryotic PSI core complexes and eukaryotic PSI supercomplexes with attached antenna clusters (PSI-LHCI)-deposited on SIF substrates.


Assuntos
Carotenoides/metabolismo , Clorofila A/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Prata/química , Formaldeído/química , Glucose/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Espectrometria de Fluorescência/métodos
18.
Nat Commun ; 11(1): 1295, 2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32157079

RESUMO

Plants prevent photodamage under high light by dissipating excess energy as heat. Conformational changes of the photosynthetic antenna complexes activate dissipation by leveraging the sensitivity of the photophysics to the protein structure. The mechanisms of dissipation remain debated, largely due to two challenges. First, because of the ultrafast timescales and large energy gaps involved, measurements lacked the temporal or spectral requirements. Second, experiments have been performed in detergent, which can induce non-native conformations, or in vivo, where contributions from homologous antenna complexes cannot be disentangled. Here, we overcome both challenges by applying ultrabroadband two-dimensional electronic spectroscopy to the principal antenna complex, LHCII, in a near-native membrane. Our data provide evidence that the membrane enhances two dissipative pathways, one of which is a previously uncharacterized chlorophyll-to-carotenoid energy transfer. Our results highlight the sensitivity of the photophysics to local environment, which may control the balance between light harvesting and dissipation in vivo.


Assuntos
Carotenoides/metabolismo , Membrana Celular/metabolismo , Clorofila/metabolismo , Transferência de Energia , Complexos de Proteínas Captadores de Luz/metabolismo , Nanoestruturas/química , Complexos de Proteínas Captadores de Luz/química , Conformação Proteica
19.
Sci Adv ; 6(10): eaaw9183, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32181334

RESUMO

Fucoxanthin and its derivatives are the main light-harvesting pigments in the photosynthetic apparatus of many chromalveolate algae and represent the most abundant carotenoids in the world's oceans, thus being major facilitators of marine primary production. A central step in fucoxanthin biosynthesis that has been elusive so far is the conversion of violaxanthin to neoxanthin. Here, we show that in chromalveolates, this reaction is catalyzed by violaxanthin de-epoxidase-like (VDL) proteins and that VDL is also involved in the formation of other light-harvesting carotenoids such as peridinin or vaucheriaxanthin. VDL is closely related to the photoprotective enzyme violaxanthin de-epoxidase that operates in plants and most algae, revealing that in major phyla of marine algae, an ancient gene duplication triggered the evolution of carotenoid functions beyond photoprotection toward light harvesting.


Assuntos
Proteínas de Algas/genética , Complexos de Proteínas Captadores de Luz/genética , Oxirredutases/genética , Feófitas/enzimologia , Xantofilas/metabolismo , Proteínas de Algas/metabolismo , Organismos Aquáticos , Carotenoides/metabolismo , Clorofila A/metabolismo , Regulação da Expressão Gênica , Complexos de Proteínas Captadores de Luz/metabolismo , Oxirredutases/metabolismo , Feófitas/classificação , Feófitas/genética , Filogenia
20.
Proc Natl Acad Sci U S A ; 117(12): 6502-6508, 2020 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-32139606

RESUMO

Carotenoids play a number of important roles in photosynthesis, primarily providing light-harvesting and photoprotective energy dissipation functions within pigment-protein complexes. The carbon-carbon double bond (C=C) conjugation length of carotenoids (N), generally between 9 and 15, determines the carotenoid-to-(bacterio)chlorophyll [(B)Chl] energy transfer efficiency. Here we purified and spectroscopically characterized light-harvesting complex 2 (LH2) from Rhodobacter sphaeroides containing the N = 7 carotenoid zeta (ζ)-carotene, not previously incorporated within a natural antenna complex. Transient absorption and time-resolved fluorescence show that, relative to the lifetime of the S1 state of ζ-carotene in solvent, the lifetime decreases ∼250-fold when ζ-carotene is incorporated within LH2, due to transfer of excitation energy to the B800 and B850 BChls a These measurements show that energy transfer proceeds with an efficiency of ∼100%, primarily via the S1 → Qx route because the S1 → S0 fluorescence emission of ζ-carotene overlaps almost perfectly with the Qx absorption band of the BChls. However, transient absorption measurements performed on microsecond timescales reveal that, unlike the native N ≥ 9 carotenoids normally utilized in light-harvesting complexes, ζ-carotene does not quench excited triplet states of BChl a, likely due to elevation of the ζ-carotene triplet energy state above that of BChl a These findings provide insights into the coevolution of photosynthetic pigments and pigment-protein complexes. We propose that the N ≥ 9 carotenoids found in light-harvesting antenna complexes represent a vital compromise that retains an acceptable level of energy transfer from carotenoids to (B)Chls while allowing acquisition of a new, essential function, namely, photoprotective quenching of harmful (B)Chl triplets.


Assuntos
Proteínas de Bactérias/metabolismo , Bacterioclorofilas/metabolismo , Carotenoides/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Proteínas de Bactérias/química , Carotenoides/química , Transferência de Energia , Cinética , Complexos de Proteínas Captadores de Luz/química , Fotossíntese , Rhodobacter sphaeroides/química , Rhodobacter sphaeroides/metabolismo
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