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1.
Int J Mol Sci ; 22(14)2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-34299206

RESUMO

Despite the intensive investigation of the molecular mechanism of skeletal muscle hypertrophy, the underlying signaling processes are not completely understood. Therefore, we used an overload model, in which the main synergist muscles (gastrocnemius, soleus) of the plantaris muscle were surgically removed, to cause a significant overload in the remaining plantaris muscle of 8-month-old Wistar male rats. SIRT1-associated pro-anabolic, pro-catabolic molecular signaling pathways, NAD and H2S levels of this overload-induced hypertrophy were studied. Fourteen days of overload resulted in a significant 43% (p < 0.01) increase in the mass of plantaris muscle compared to sham operated animals. Cystathionine-ß-synthase (CBS) activities and bioavailable H2S levels were not modified by overload. On the other hand, overload-induced hypertrophy of skeletal muscle was associated with increased SIRT1 (p < 0.01), Akt (p < 0.01), mTOR, S6 (p < 0.01) and suppressed sestrin 2 levels (p < 0.01), which are mostly responsible for anabolic signaling. Decreased FOXO1 and SIRT3 signaling (p < 0.01) suggest downregulation of protein breakdown and mitophagy. Decreased levels of NAD+, sestrin2, OGG1 (p < 0.01) indicate that the redox milieu of skeletal muscle after 14 days of overloading is reduced. The present investigation revealed novel cellular interactions that regulate anabolic and catabolic processes in the hypertrophy of skeletal muscle.


Assuntos
Cistationina beta-Sintase/metabolismo , Proteínas Musculares/metabolismo , Músculo Esquelético/patologia , Animais , Hipertrofia/genética , Hipertrofia/metabolismo , Hipertrofia/patologia , Masculino , Proteínas Musculares/genética , Músculo Esquelético/metabolismo , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/antagonistas & inibidores , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos , Ratos Wistar , Proteínas Quinases S6 Ribossômicas/genética , Proteínas Quinases S6 Ribossômicas/metabolismo , Sirtuína 1/genética , Sirtuína 1/metabolismo , Sirtuínas/antagonistas & inibidores , Sirtuínas/genética , Sirtuínas/metabolismo , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo
2.
Front Plant Sci ; 11: 547818, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33193480

RESUMO

Membrane-bound or cytosolic light-sensitive proteins, playing a crucial role in energy- and signal-transduction processes of various photosynthetic microorganisms, have been optimized for sensing or harvesting light by myriads of years of evolution. Upon absorption of a photon, they undergo a usually cyclic reaction series of conformations, and the accompanying spectro-kinetic events assign robust nonlinear optical (NLO) properties for these chromoproteins. During recent years, they have attracted a considerable interest among researchers of the applied optics community as well, where finding the appropriate NLO material for a particular application is a pivotal task. Potential applications have emerged in various branches of photonics, including optical information storage and processing, higher-harmonic and white-light continuum generation, or biosensorics. In our earlier work, we also raised the possibility of using chromoproteins, such as bacteriorhodopsin (bR), as building blocks for the active elements of integrated optical (IO) circuits, where several organic and inorganic photonic materials have been considered as active components, but so far none of them has been deemed ideal for the purpose. In the current study, we investigate the linear and NLO properties of biofilms made of photoactive yellow protein (PYP) and bR. The kinetics of the photoreactions are monitored by time-resolved absorption experiments, while the refractive index of the films and its light-induced changes are measured using the Optical Waveguide Lightmode Spectroscopy (OWLS) and Z-scan techniques, respectively. The nonlinear refractive index and the refractive index change of both protein films were determined in the green spectral range in a wide range of intensities and at various laser repetition rates. The nonlinear refractive index and refractive index change of PYP were compared to those of bR, with respect to photonics applications. Our results imply that the NLO properties of these proteins make them promising candidates for utilization in applied photonics, and they should be considered as valid alternatives for active components of IO circuits.

3.
J Sport Health Sci ; 9(5): 405-414, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32780693

RESUMO

MicroRNAs (miRs) are small regulatory RNA transcripts capable of post-transcriptional silencing of mRNA messages by entering a cellular bimolecular apparatus called RNA-induced silencing complex. miRs are involved in the regulation of cellular processes producing, eliminating or repairing the damage caused by reactive oxygen species, and they are active players in redox homeostasis. Increased mitochondrial biogenesis, function and hypertrophy of skeletal muscle are important adaptive responses to regular exercise. In the present review, we highlight some of the redox-sensitive regulatory roles of miRs.


Assuntos
Adaptação Fisiológica , Exercício Físico/fisiologia , MicroRNAs/metabolismo , Músculo Esquelético/metabolismo , Oxirredução , Animais , Humanos , Biogênese de Organelas , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais
4.
Photosynth Res ; 145(2): 179-188, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32720110

RESUMO

The major light-harvesting system in cyanobacteria, the phycobilisome, is an essential component of the photosynthetic apparatus that regulates the utilization of the natural light source-the Sun. Earlier works revealed that the thylakoid membrane composition and its physical properties might have an important role in antennas docking. Polyunsaturated lipids and xanthophylls are among the most significant modulators of the physical properties of thylakoid membranes. In the nature, the action of these molecules is orchestrated in response to environmental stimuli among which the growth temperature is the most influential. In order to further clarify the significance of thylakoid membrane physical properties for the phycobilisomes assembly (i.e. structural integrity) and their ability to efficiently direct the excitation energy towards the photosynthetic complexes, in this work, we utilize cyanobacterial Synechocystis sp. PCC 6803 mutants deficient in polyunsaturated lipids (AD mutant) and xanthophylls (RO mutant), as well as a strain depleted of both xanthophylls and polyunsaturated lipids (ROAD multiple mutant). For the first time, we discuss the effect of those mutations on the phycobilisomes assembly, integrity and functionality at optimal (30 °C) and moderate low (25 °C) and high (35 °C) temperatures. Our results show that xanthophyll depletion exerts a much stronger effect on both phycobilisome's integrity and the response of cells to growth at suboptimal temperatures than lipid unsaturation level. The strongest effects were observed for the combined ROAD mutant, which exhibited thermally destabilized phycobilisomes and a population of energetically uncoupled phycocyanin units.


Assuntos
Carotenoides/metabolismo , Fotossíntese , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Ficobilissomas/metabolismo , Synechocystis/metabolismo , Metabolismo dos Lipídeos , Mutação , Ficocianina/metabolismo , Synechocystis/genética , Temperatura , Tilacoides/metabolismo , Xantofilas/metabolismo
5.
Photosynth Res ; 143(3): 251-262, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31848802

RESUMO

In Synechocystis sp. PCC 6803 and some other cyanobacteria photosystem I reaction centres exist predominantly as trimers, with minor contribution of monomeric form, when cultivated at standard optimized conditions. In contrast, in plant chloroplasts photosystem I complex is exclusively monomeric. The functional significance of trimeric organization of cyanobacterial photosystem I remains not fully understood. In this study, we compared the photosynthetic characteristics of PSI in wild type and psaL knockout mutant. The results show that relative to photosystem I trimer in wild-type cells, photosystem I monomer in psaL- mutant has a smaller P700+ pool size under low and moderate light, slower P700 oxidation upon dark-to-light transition, and slower P700+ reduction upon light-to-dark transition. The mutant also shows strongly diminished photosystem I donor side limitations [quantum yield Y(ND)] at low, moderate and high light, but enhanced photosystem I acceptor side limitations [quantum yield Y(NA)], especially at low light (22 µmol photons m-2 s-1). In line with these functional characteristics are the determined differences in the relative expression genes encoding of selected electron transporters. The psaL- mutant showed significant (ca fivefold) upregulation of the photosystem I donor cytochrome c6, and downregulation of photosystem I acceptors (ferredoxin, flavodoxin) and proteins of alternative electron flows originating in photosystem I acceptor side. Taken together, our results suggest that photosystem I trimerization in wild-type Synechocystis cells plays a role in the protection of photosystem I from photoinhibition via maintaining enhanced donor side electron transport limitations and minimal acceptor side electron transport limitations at various light intensities.


Assuntos
Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Multimerização Proteica , Synechocystis/metabolismo , Proteínas de Bactérias/metabolismo , Transporte de Elétrons/efeitos da radiação , Regulação Bacteriana da Expressão Gênica/efeitos da radiação , Cinética , Luz , Proteínas de Membrana/metabolismo , Mutação/genética , Oxirredução , Estresse Oxidativo/efeitos da radiação , Fotossíntese/efeitos da radiação , Ficobilissomas/metabolismo , Ficobilissomas/efeitos da radiação , Teoria Quântica , Espectrometria de Fluorescência , Synechocystis/genética , Synechocystis/efeitos da radiação , Tilacoides/metabolismo
6.
Biochim Biophys Acta Mol Cell Biol Lipids ; 1864(10): 1384-1395, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31228574

RESUMO

In cyanobacteria, increasing growth temperature decreases lipid unsaturation and the ratio of monomer/trimer photosystem I (PSI) complexes. In the present study we applied Fourier-transform infrared (FTIR) spectroscopy and lipidomic analysis to study the effects of PSI monomer/oligomer ratio on the physical properties and lipid composition of thylakoids. To enhance the presence of monomeric PSI, a Synechocystis sp. PCC6803/ΔpsaL mutant strain (PsaL) was used which, unlike both trimeric and monomeric PSI-containing wild type (WT) cells, contain only the monomeric form. The protein-to-lipid ratio remained unchanged in the mutant but, due to an increase in the lipid disorder in its thylakoids, the gel to liquid-crystalline phase transition temperature (Tm) is lower than in the WT. In thylakoid membranes of the mutant, digalactosyldiacylglycerol (DGDG), the most abundant bilayer-forming lipid is accumulated, whereas those in the WT contain more monogalactosyldiacylglycerol (MGDG), the only non-bilayer-forming lipid in cyanobacteria. In PsaL cells, the unsaturation level of sulphoquinovosyldiacylglycerol (SQDG), a regulatory anionic lipid, has increased. It seems that merely a change in the oligomerization level of a membrane protein complex (PSI), and thus the altered protein-lipid interface, can affect the lipid composition and, in addition, the whole dynamics of the membrane. Singular value decomposition (SVD) analysis has shown that in PsaL thylakoidal protein-lipid interactions are less stable than in the WT, and proteins start losing their native secondary structure at much milder lipid packing perturbations. Conclusions drawn from this system should be generally applicable for protein-lipid interactions in biological membranes.


Assuntos
Proteínas de Bactérias/metabolismo , Metabolismo dos Lipídeos , Complexo de Proteína do Fotossistema I/metabolismo , Synechocystis/metabolismo , Lipidômica , Lipídeos/análise , Multimerização Proteica , Synechocystis/química
7.
J Sport Health Sci ; 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-32813644

RESUMO

PURPOSE: Blood flow restriction (BFR) with low-intensity resistance training has been shown to result in hypertrophy of skeletal muscle. In this study, we tested the hypothesis that BFR during the rest periods between acute, high-intensity resistance exercise sessions (70% of 1 repetition maximum, 7 sets with 10 repetitions) enhances the effects of the resistance training. METHODS: A total of 7 healthy young men performed squats, and between sets BFR was carried out on 1 leg while the other leg served as a control. Because BFR was applied during rest periods, even severe occlusion pressure (approximately 230 mm Hg), which almost completely blocked blood flow, was well-tolerated by the participants. Five muscle-specific microRNAs were measured from the biopsy samples, which were taken 2 h after the acute training. RESULTS: Doppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR. MicroRNA-206 levels significantly decreased in the BFR leg compared to the control. The mRNA levels of RAC-ß serine/threonine-protein kinase v22, nuclear respiratory factor 1, vascular endothelial growth factor, lupus Ku autoantigen protein p70 genes (p < 0.05), and paired box 7 (p < 0.01) increased in the BFR leg. The protein levels of paired box 7, nuclear respiratory factor 1, and peroxisome proliferator-activated receptor γ coactivator 1α did not differ between the BFR leg and the control leg. CONCLUSION: Data revealed that BFR, during the rest periods of high-load resistance training, could lead to mRNA elevation of those proteins that regulate angiogenesis, mitochondrial biogenesis, and muscle hypertrophy and repair. However, BFR also can cause DNA damage, judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.

8.
J Plant Physiol ; 223: 96-104, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29558689

RESUMO

Phosphatidylglycerol is an essential phospholipid for photosynthesis and other cellular processes. We investigated the role of phosphatidylglycerol in cell division and metabolism in a phophatidylglycerol-auxotrophic strain of Synechococcus PCC7942. Here we show that phosphatidylglycerol is essential for the photosynthetic electron transfer and for the oligomerisation of the photosynthetic complexes, notably, we revealed that this lipid is important for non-linear electron transport. Furthermore, we demonstrate that phosphatidylglycerol starvation elevated the expressions of proteins of nitrogen and carbon metabolism. Moreover, we show that phosphatidylglycerol-deficient cells changed the morphology, became elongated, the FtsZ ring did not assemble correctly, and subsequently the division was hindered. However, supplementation with phosphatidylglycerol restored the ring-like structure at the mid-cell region and the normal cell size, demonstrating the phosphatidylglycerol is needed for normal septum formation. Taken together, central roles of phosphatidylglycerol were revealed; it is implicated in the photosynthetic activity, the metabolism and the fission of bacteria.


Assuntos
Divisão Celular , Fosfatidilgliceróis/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Synechococcus/fisiologia , Transporte de Elétrons
9.
Photosynth Res ; 137(1): 95-104, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29322483

RESUMO

Phycobilisomes (PBSs) are supramolecular pigment-protein complexes that serve as light-harvesting antennae in cyanobacteria. They are built up by phycobiliproteins assembled into allophycocyanin core cylinders (ensuring the physical interaction with the photosystems) and phycocyanin rods (protruding from the cores and having light-harvesting function), the whole PBSs structure being maintained by linker proteins. PBSs play major role in light-harvesting optimization in cyanobacteria; therefore, the characterization of their structural integrity in intact cells is of great importance. The present study utilizes differential scanning calorimetry and spectroscopy techniques to explore for the first time, the thermodynamic stability of PBSs in intact Synechocystis sp. PCC 6803 cells and to probe its alteration as a result of mutations or under different growth conditions. As a first step, we characterize the thermodynamic behavior of intact and dismantled PBSs isolated from wild-type cells (having fully assembled PBSs) and from CK mutant cells (that lack phycocyanin rods and contain only allophycocyanin cores), and identified the thermal transitions of phycocyanin and allophycocyanin units in vitro. Next, we demonstrate that in intact cells PBSs exhibit sharp, high amplitude thermal transition at about 63 °C that strongly depends on the structural integrity of the PBSs supercomplex. Our findings implicate that calorimetry could offer a valuable approach for the assessment of the influence of variety of factors affecting the stability and structural organization of phycobilisomes in intact cyanobacterial cells.


Assuntos
Ficobilissomas/química , Synechocystis/química , Varredura Diferencial de Calorimetria , Mutação , Synechocystis/genética , Termodinâmica
10.
Biochim Biophys Acta Bioenerg ; 1858(7): 510-518, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28478116

RESUMO

The function of xanthophylls in the organisation and structure of the photosynthetic complexes is not completely clarified yet. Recently, we observed a reduced level of the photosystem oligomers upon xanthophyll deficiency, although xanthophylls are not considered to be part of the photosynthetic complexes of cyanobacteria. The present study aimed at further investigating the relationship between xanthophylls and photosytem I (PSI) complex in the cyanobacterium Synechocystis sp. PCC 6803. Interestingly, we recorded the presence of echinenone and zeaxanthin in the isolated PSI trimers. These two xanthophyll species are among the most abundant xanthophylls in this cyanobacterial species. Various xanthophyll biosynthesis mutants were used to investigate the specific role of these xanthophylls. Our spectroscopic results revealed specific structural changes manifested in altered pigment-pigment or pigment-protein interactions within PSI complex in the absence of zeaxanthin and echinenone. These structural modifications of the complexes seem to destabilize the PSI trimeric complexes and eventually result in an increased propensity for monomerization. Our results clearly demonstrate that xanthophylls are important for the fine-tuning of the PSI trimer structure. These xanthophylls could be part of the complex or be embedded in the membrane in the vicinity of PSI.


Assuntos
Proteínas de Bactérias/química , Carotenoides/fisiologia , Complexo de Proteína do Fotossistema I/química , Synechocystis/metabolismo , Zeaxantinas/fisiologia , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/metabolismo , Centrifugação com Gradiente de Concentração , Dicroísmo Circular , Complexo de Proteína do Fotossistema I/isolamento & purificação , Complexo de Proteína do Fotossistema I/metabolismo , Pigmentos Biológicos/análise , Ligação Proteica , Multimerização Proteica , Espectrometria de Fluorescência , Tilacoides/química , beta Caroteno/análise
11.
Biochim Biophys Acta Bioenerg ; 1858(5): 337-350, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28188782

RESUMO

Polyunsaturated lipids are important components of photosynthetic membranes. Xanthophylls are the main photoprotective agents, can assist in protection against light stress, and are crucial in the recovery from photoinhibition. We generated the xanthophyll- and polyunsaturated lipid-deficient ROAD mutant of Synechocystis sp. PCC6803 (Synechocystis) in order to study the little-known cooperative effects of lipids and carotenoids (Cars). Electron microscopic investigations confirmed that in the absence of xanthophylls the S-layer of the cellular envelope is missing. In wild-type (WT) cells, as well as the xanthophyll-less (RO), polyunsaturated lipid-less (AD), and the newly constructed ROAD mutants the lipid and Car compositions were determined by MS and HPLC, respectively. We found that, relative to the WT, the lipid composition of the mutants was remodeled and the Car content changed accordingly. In the mutants the ratio of non-bilayer-forming (NBL) to bilayer-forming (BL) lipids was found considerably lower. Xanthophyll to ß-carotene ratio increased in the AD mutant. In vitro and in vivo methods demonstrated that saturated, monounsaturated lipids and xanthophylls may stabilize the trimerization of Photosystem I (PSI). Fluorescence induction and oxygen-evolving activity measurements revealed increased light sensitivity of RO cells compared to those of the WT. ROAD showed a robust increase in light susceptibility and reduced recovery capability, especially at moderate low (ML) and moderate high (MH) temperatures, indicating a cooperative effect of xanthophylls and polyunsaturated lipids. We suggest that both lipid unsaturation and xanthophylls are required for providing the proper structure and functioning of the membrane environment that protects against light and temperature stress.


Assuntos
Membrana Celular/efeitos da radiação , Luz , Lipídeos de Membrana/efeitos da radiação , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/efeitos da radiação , Estresse Fisiológico , Synechocystis/efeitos da radiação , Temperatura , Xantofilas/efeitos da radiação , Adaptação Fisiológica , Membrana Celular/genética , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Genótipo , Metabolismo dos Lipídeos/genética , Metabolismo dos Lipídeos/efeitos da radiação , Lipídeos de Membrana/metabolismo , Mutação , Fenótipo , Fotossíntese/genética , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema I/metabolismo , Synechocystis/genética , Synechocystis/metabolismo , Synechocystis/ultraestrutura , Tilacoides/metabolismo , Tilacoides/efeitos da radiação , Fatores de Tempo , Xantofilas/genética , Xantofilas/metabolismo , beta Caroteno/metabolismo , beta Caroteno/efeitos da radiação
12.
Photosynth Res ; 130(1-3): 403-415, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27165097

RESUMO

We investigated the relation between the carotenoid composition and the structure of phycobilisome (PBS) antenna of cyanobacterium Synechocystis sp. PCC 6803. PBS is a large soluble protein complex enhances the light harvesting efficiency of the cells. It is composed of a central allophycocyanin core and radial phycocyanin rods, but it does not contain carotenoids. However, the absence or low level of carotenoids were previously shown to lead the co-existence of unconnected rod units and assembled PBS with shorter peripheral rods. Here we show that the lack of ß-carotene, but not of xanthophylls or the distortion of photosystem structure, evoked unconnected rods. Thus, these essential ß-carotene molecules are not bound by Photosystem I or Photosystem II. Our results do not show correlation between the reactive oxygen species (ROS) and PBS distortion despite the higher singlet oxygen producing capacity and light sensitivity of the mutant cells. Reduced cellular level of those linker proteins attaching the rod units together was also observed, but the direct damage of the linkers by ROS are not supported by our data. Enzymatic PBS proteolysis induced by nitrogen starvation in carotenoid mutant cells revealed a retarded degradation of the unconnected rod units.


Assuntos
Complexos de Proteínas Captadores de Luz/efeitos dos fármacos , Ficobilissomas/efeitos dos fármacos , Synechocystis/efeitos dos fármacos , beta Caroteno/farmacologia , Glucose/metabolismo , Luz , Complexos de Proteínas Captadores de Luz/fisiologia , Nitrogênio/metabolismo , Fotossíntese/efeitos dos fármacos , Ficobilissomas/isolamento & purificação , Ficobilissomas/fisiologia , Espectrometria de Fluorescência , Synechocystis/fisiologia
13.
Acta Crystallogr F Struct Biol Commun ; 72(Pt 4): 276-81, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-27050260

RESUMO

Calexcitin was first identified in the marine snail Hermissenda crassicornis as a neuronal-specific protein that becomes upregulated and phosphorylated in associative learning. Calexcitin possesses four EF-hand motifs, but only the first three (EF-1 to EF-3) are involved in binding metal ions. Past work has indicated that under physiological conditions EF-1 and EF-2 bind Mg(2+) and Ca(2+), while EF-3 is likely to bind only Ca(2+). The fourth EF-hand is nonfunctional owing to a lack of key metal-binding residues. The aim of this study was to use a crystallographic approach to determine which of the three metal-binding sites of calexcitin is most readily replaced by exogenous metal ions, potentially shedding light on which of the EF-hands play a `sensory' role in neuronal calcium signalling. By co-crystallizing recombinant calexcitin with equimolar Gd(3+) in the presence of trace Ca(2+), EF-1 was shown to become fully occupied by Gd(3+) ions, while the other two sites remain fully occupied by Ca(2+). The structure of the Gd(3+)-calexcitin complex has been refined to an R factor of 21.5% and an Rfree of 30.4% at 2.2 Šresolution. These findings suggest that EF-1 of calexcitin is the Ca(2+)-binding site with the lowest selectivity for Ca(2+), and the implications of this finding for calcium sensing in neuronal signalling pathways are discussed.


Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Cálcio/metabolismo , Gadolínio/metabolismo , Neurônios/metabolismo , Transdução de Sinais , Sítios de Ligação , Cristalização , Cristalografia por Raios X
14.
Front Plant Sci ; 7: 295, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27014318

RESUMO

Carotenoids (carotenes and xanthophylls) are ubiquitous constituents of living organisms. They are protective agents against oxidative stresses and serve as modulators of membrane microviscosity. As antioxidants they can protect photosynthetic organisms from free radicals like reactive oxygen species that originate from water splitting, the first step of photosynthesis. We summarize the structural and functional roles of carotenoids in connection with cyanobacterial Photosystem II. Although carotenoids are hydrophobic molecules, their complexes with proteins also allow cytoplasmic localization. In cyanobacterial cells such complexes are called orange carotenoid proteins, and they protect Photosystem II and Photosystem I by preventing their overexcitation through phycobilisomes (PBS). Recently it has been observed that carotenoids are not only required for the proper functioning, but also for the structural stability of PBSs.

15.
Plant Physiol ; 169(2): 1307-17, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26269547

RESUMO

The negatively charged lipid phosphatidylglycerol (PG) constitutes up to 10% of total lipids in photosynthetic membranes, and its deprivation in cyanobacteria is accompanied by chlorophyll (Chl) depletion. Indeed, radioactive labeling of the PG-depleted ΔpgsA mutant of Synechocystis sp. strain PCC 6803, which is not able to synthesize PG, proved the inhibition of Chl biosynthesis caused by restriction on the formation of 5-aminolevulinic acid and protochlorophyllide. Although the mutant accumulated chlorophyllide, the last Chl precursor, we showed that it originated from dephytylation of existing Chl and not from the block in the Chl biosynthesis. The lack of de novo-produced Chl under PG depletion was accompanied by a significantly weakened biosynthesis of both monomeric and trimeric photosystem I (PSI) complexes, although the decrease in cellular content was manifested only for the trimeric form. However, our analysis of ΔpgsA mutant, which lacked trimeric PSI because of the absence of the PsaL subunit, suggested that the virtual stability of monomeric PSI is a result of disintegration of PSI trimers. Interestingly, the loss of trimeric PSI was accompanied by accumulation of monomeric PSI associated with the newly synthesized CP43 subunit of photosystem II. We conclude that the absence of PG results in the inhibition of Chl biosynthetic pathway, which impairs synthesis of PSI, despite the accumulation of chlorophyllide released from the degraded Chl proteins. Based on the knowledge about the role of PG in prokaryotes, we hypothesize that the synthesis of Chl and PSI complexes are colocated in a membrane microdomain requiring PG for integrity.


Assuntos
Clorofila/biossíntese , Clorofilídeos/metabolismo , Fosfatidilgliceróis/metabolismo , Synechocystis/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Carbono-Oxigênio Ligases/metabolismo , Clorofila/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Fosfatidilgliceróis/genética , Complexo de Proteína do Fotossistema I/metabolismo , Protoclorifilida/metabolismo , Synechocystis/genética , Transferases (Outros Grupos de Fosfato Substituídos)/genética , Transferases (Outros Grupos de Fosfato Substituídos)/metabolismo
16.
Biochim Biophys Acta ; 1847(10): 1153-65, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26045333

RESUMO

In photosynthetic organisms, carotenoids (carotenes and xanthophylls) are important for light harvesting, photoprotection and structural stability of a variety of pigment-protein complexes. Here, we investigated the consequences of altered carotenoid composition for the functional organization of photosynthetic complexes in wild-type and various mutant strains of the cyanobacterium Synechocystis sp. PCC 6803. Although it is generally accepted that xanthophylls do not play a role in cyanobacterial photosynthesis in low-light conditions, we have found that the absence of xanthophylls leads to reduced oligomerization of photosystems I and II. This is remarkable because these complexes do not bind xanthophylls. Oligomerization is even more disturbed in crtH mutant cells, which show limited carotenoid synthesis; in these cells also the phycobilisomes are distorted despite the fact that these extramembranous light-harvesting complexes do not contain carotenoids. The number of phycocyanin rods connected to the phycobilisome core is strongly reduced leading to high amounts of unattached phycocyanin units. In the absence of carotenoids the overall organization of the thylakoid membranes is disturbed: Photosystem II is not formed, photosystem I hardly oligomerizes and the assembly of phycobilisomes remains incomplete. These data underline the importance of carotenoids in the structural and functional organization of the cyanobacterial photosynthetic machinery.

17.
Plant Cell Physiol ; 56(3): 558-71, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25520404

RESUMO

In the thylakoid membranes of the mesophilic cyanobacterium Synechocystis PCC6803, PSI reaction centers (RCs) are organized as monomers and trimers. PsaL, a 16 kDa hydrophobic protein, a subunit of the PSI RC, was previously identified as crucial for the formation of PSI trimers. In this work, the physiological effects accompanied by PSI oligomerization were studied using a PsaL-deficient mutant (ΔpsaL), not able to form PSI trimers, grown at various temperatures. We demonstrate that in wild-type Synechocystis, the monomer to trimer ratio depends on the growth temperature. The inactivation of the psaL gene in Synechocystis grown phototropically at 30°C induces profound morphological changes, including the accumulation of glycogen granules localized in the cytoplasm, resulting in the separation of particular thylakoid layers. The carotenoid composition in ΔpsaL shows that PSI monomerization leads to an increased accumulation of myxoxantophyll, zeaxanthin and echinenone irrespective of the temperature conditions. These xanthophylls are formed at the expense of ß-carotene. The measured H2O→CO2 oxygen evolution rates in the ΔpsaL mutant are higher than those observed in the wild type, irrespective of the growth temperature. Moreover, circular dichroism spectroscopy in the visible range reveals that a peak attributable to long-wavelength-absorbing carotenoids is apparently enhanced in the trimer-accumulating wild-type cells. These results suggest that specific carotenoids are accompanied by the accumulation of PSI oligomers and play a role in the formation of PSI oligomer structure.


Assuntos
Temperatura Alta , Complexo de Proteína do Fotossistema I/metabolismo , Multimerização Proteica , Synechocystis/crescimento & desenvolvimento , Synechocystis/metabolismo , Xantofilas/biossíntese , Processos Autotróficos , Carotenoides/metabolismo , Cromatografia por Troca Iônica , Dicroísmo Circular , Inativação Gênica , Genes Bacterianos , Teste de Complementação Genética , Mutação/genética , Oxigênio/metabolismo , Processos Fototróficos , Synechocystis/citologia , Synechocystis/ultraestrutura , Tilacoides/metabolismo
18.
Proteomics ; 14(9): 1053-7, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24574175

RESUMO

We present a proteomics dataset combining SDS-PAGE prefractionation and data-dependent LC-MS/MS that enables the identification of phosphatidylglycerol-regulated proteins in the pgsA(-) mutant of Synechocystis sp. PCC6803, a cyanobacterium strain that grows with this indispensable phospholipid added exogenously. We searched the acquired raw data against a composite protein sequence database of Synechocystis using MASCOT, and employed Progenesis LC-MS software for label-free quantification based on extracted peptide intensities to detect changes in protein abundances upon phospholipid withdrawal. Protein identifications were validated using rigorous criteria, and our analysis of the dataset revealed 80 phosphatidylglycerol-regulated proteins involved in various cellular processes including photosynthesis, respiration, metabolism, transport, transcription, and translation. The data have been deposited to the ProteomeXchange with identifier PXD000363 (http://proteomecentral.proteomexchange.org/dataset/PXD000363).


Assuntos
Proteínas de Bactérias/análise , Fosfatidilgliceróis/metabolismo , Proteoma/análise , Proteômica/métodos , Synechocystis/química , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Cromatografia Líquida/métodos , Proteoma/química , Proteoma/metabolismo , Synechocystis/metabolismo , Espectrometria de Massas em Tandem/métodos
19.
Prog Lipid Res ; 52(4): 539-61, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23896007

RESUMO

Carotenoids (CARs) are a group of pigments that perform several important physiological functions in all kingdoms of living organisms. CARs serve as protective agents, which are essential structural components of photosynthetic complexes and membranes, and they play an important role in the light harvesting mechanism of photosynthesizing plants and cyanobacteria. The protection against reactive oxygen species, realized by quenching of singlet oxygen and the excited states of photosensitizing molecules, as well as by the scavenging of free radicals, is one of the main biological functions of CARs. X-ray crystallographic localization of CARs revealed that they are present at functionally and structurally important sites of both the PSI and PSII reaction centers. Characterization of a CAR-less cyanobacterial mutant revealed that while the absence of CARs prevents the formation of PSII complexes, it does not abolish the assembly and function of PSI. CAR molecules assist in the formation of protein subunits of the photosynthetic complexes by gluing together their protein components. In addition to their aforementioned indispensable functions, CARs have a substantial role in the formation and maintenance of proper cellular architecture, and potentially also in the protection of the translational machinery under stress conditions.


Assuntos
Carotenoides/biossíntese , Oxigênio/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Carotenoides/química , Cianobactérias/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/química , Substâncias Protetoras/química , Substâncias Protetoras/metabolismo , Xantofilas/biossíntese , Xantofilas/química
20.
Physiol Plant ; 147(2): 248-60, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22582961

RESUMO

Influence of the modification of the cyanobacterial light-harvesting complex [i.e. phycobilisomes (PBS)] on the surface electric properties and the functions of photosynthetic membranes was investigated. We used four PBS mutant strains of Synechocystis sp. PCC6803 as follows: PAL (PBS-less), CK (phycocyanin-less), BE (PSII-PBS-less) and PSI-less/apcE(-) (PSI-less with detached PBS). Modifications of the PBS content lead to changes in the cell morphology and surface electric properties of the thylakoid membranes as well as in their functions, such as photosynthetic oxygen-evolving activity, P700 kinetics and energy transfer between the pigment-protein complexes. Data reveal that the complete elimination of PBS in the PAL mutant causes a slight decrease in the electric dipole moments of the thylakoid membranes, whereas significant perturbations of the surface charges were registered in the membranes without assembled PBS-PSII macrocomplex (BE mutant) or PSI complex (PSI-less mutant). These observations correlate with the detected alterations in the membrane structural organization. Using a polarographic oxygen rate electrode, we showed that the ratio of the fast to the slow oxygen-evolving PSII centers depends on the partial or complete elimination of light-harvesting complexes, as the slow operating PSII centers dominate in the PBS-less mutant and in the mutant with detached PBS.


Assuntos
Fotossíntese , Complexo de Proteína do Fotossistema I/fisiologia , Complexo de Proteína do Fotossistema II/fisiologia , Synechocystis/genética , Tilacoides/fisiologia , Fenômenos Eletrofisiológicos , Deleção de Genes , Microscopia Eletrônica , Oxirredução , Oxigênio/análise , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema II/genética , Synechocystis/fisiologia , Synechocystis/ultraestrutura
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