| 1. |
- Funk, Christiane, et al.
(författare)
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High-light stress and the one-helix LHC-like proteins of the cryptophyte Guillardia theta
- 2011
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1807:7, s. 841-846
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Tidskriftsartikel (refereegranskat)abstract
- Cryptophytes like the cryptomonad Guillardia theta are part of the marine phytoplankton and therefore major players in global carbon and biogeochemical cycles. Despite the importance for the cell in being able to cope with large changes in illumination on a daily basis, very little is known about photoprotection mechanisms in cryptophytes. Here we show that G. theta is able to perform non-photochemical quenching, although none of the usual xanthophyll cycle pigments (e.g. zeaxanthin, diadinoxanthin, diatoxanthin) are present at detectable levels. Instead, acclimation to high light intensity seems to involve an increase of alloxanthin. G. theta has genes for two one-helix "light-harvesting-like" proteins, related to some cyanobacterial genes which are induced in response to high light stress. Both the plastid-encoded gene (hlipP) and the nucleomorph-encoded gene (HlipNm) are expressed, but transcript levels decrease rather than increase during high light exposure, suggesting they are not involved in a high light stress response. The HlipNm protein was detected with a specific antibody; expression was constant, independent of the light exposure.
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| 2. |
- Hernández-Prieto, Miguel Angel, 1975-, et al.
(författare)
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Imbalance in tetrapyrrole metabolites caused by deletion of scp genes in the cyanobacterium Synechocystis sp. PCC 6803 results in dramatic cellular effects
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Light-harvsting like (Lil) proteins contain a chlorophyll-binding domain similar to the chlorophyll a/b binding antenna proteins of plants. The five small Cab-like proteins (SCPs) of the cyanobacterium Synechocystis sp. PCC 6803 belong to the Lil family. They have been shown to stabilize chlorophyll and to play a role in the tetrapyrrole biosynthesis pathway (Xu, H., Vavilin, D., Funk, C. and Vermaas, W. (2004) J. Biol. Chem. 279, 27971-27979). Here we show that deletion of the five scp genes in a PSI-less mutant results in a decrease of Photosystem II amount in the thylakoid membrane. This reduction of Photosystem II leads to increased cell volume, disorganized thylakoid membranes in the cell, and metabolic imbalance. We conclude that the lack of SCPs alters the assembly/repair of Photosystem II, causing an imbalance in the energetic level of the mutant cells.
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| 3. |
- Hernandez-Prieto, Miguel A., et al.
(författare)
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The small CAB-like proteins of the cyanobacterium Synechocystis sp. PCC 6803 : Their involvement in chlorophyll biogenesis for Photosystem II
- 2011
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier. - 0005-2728 .- 1879-2650. ; 1807:9, s. 1143-1151
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Tidskriftsartikel (refereegranskat)abstract
- The five small CAB-like proteins (ScpA-E) of the cyanobacterium Synechocystis sp. PCC 6803 belong to the family of stress-induced light-harvesting-like proteins, but are constitutively expressed in a mutant deficient of Photosystem I (PSI). Using absorption, fluorescence and thermoluminescence measurements this PSI-less strain was compared with a mutant, in which all SCPs were additionally deleted. Depletion of SCPs led to structural rearrangements in Photosystem II (PSII): less photosystems were assembled; and in these, the Q(B) site was modified. Despite the lower amount of PSII, the SCP-deficient cells contained the same amount of phycobilisomes (PBS) as the control. Although, the excess PBS were functionally disconnected, their fluorescence was quenched under high irradiance by the activated Orange Carotenoid Protein (OCP). Additionally the amount of OCP, but not of the iron-stress induced protein (isiA), was higher in this SCP-depleted mutant compared with the control. As previously described, the lack of SCPs affects the chlorophyll biosynthesis (Vavilin, D., Brune, D. C., Vermaas, W. (2005) Biochim Biophys Acta 1708, 91-101). We demonstrate that chlorophyll synthesis is required for efficient PSII repair and that it is partly impaired in the absence of SCPs. At the same time, the amount of chlorophyll also seems to influence the expression of ScpC and ScpD.
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| 4. |
- Storm, Patrik, 1966-, et al.
(författare)
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Refolding and enzyme kinetic studies on the ferrochelatase of the cyanobacterium synechocystis sp. PCC 6803
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- Heme is a cofactor for proteins participating in many important cellular processes, including respiration, oxygen metabolism and oxygen binding. The key enzyme in the heme biosynthesis pathway is ferrochelatase (protohaem ferrolyase, EC 4.99.1.1), which catalyzes the insertion of ferrous iron into protoporphyrin IX. In higher plants, the ferrochelatase enzyme is localized not only in mitochondria, but also in chloroplasts. The plastidic type II ferrochelatase contains a C-terminal chlorophyll a/b (CAB) motif, a conserved hydrophobic stretch homologous to the CAB domain of plant light harvesting proteins and light-harvesting like proteins. This type II ferrochelatase, found in all photosynthetic organisms, is presumed to have evolved from the cyanobacterial ferrochelatase. Here we describe a detailed enzymological study on recombinant, refolded and functionally active type II ferrochelatase (FeCh) from the cyanobacterium Synechocystis sp. PCC 6803. A protocol was developed for the functional refolding and purification of the recombinant enzyme from inclusion bodies, without truncation products or soluble aggregates. The refolded FeCh is active in its monomeric form, however, addition of an N-terminal His6-tag has significant effects on its enzyme kinetics. Strikingly, removal of the C-terminal CAB-domain led to a greatly increased turnover number, kcat, compared to the full length protein. While pigments isolated from photosynthetic membranes decrease the activity of FeCh, direct pigment binding to the CAB domain of FeCh was not evident.
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| 5. |
- Tibiletti, Tania, et al.
(författare)
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Deletion of the gene family of small chlorophyll-binding proteins (ScpABCDE) offsets C/N homeostasis in Synechocystis PCC 6803
- 2016
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier. - 0005-2728 .- 1879-2650. ; 1857:4, s. 396-407
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Tidskriftsartikel (refereegranskat)abstract
- In the family of chlorophyll binding proteins, single helix small CAB-like proteins (SCPs) are found in all organisms performing oxygenic photosynthesis. Here, we investigated the function of these stress-inducible proteins in the cyanobacterium Synechocystis sp. PCC 6803. We compared physiological, proteome and transcriptome traits of a Photosystem I (PSI) deletion strain, which constitutively induces SCPs, and a PSI-less/ScpABCDE− without SCPs. The SCP mutant cells were larger in size, showed irregular thylakoid structure and differed in cell-surface morphology. Deletion of scp genes strongly affected the carbon (C) and nitrogen (N) balance, resulting in accumulation of carbohydrates and a decrease in N-rich compounds (proteins and chlorophyll). Data from transcriptomic and metabolomic experiments revealed a role of SCPs in the control of chlorophyll biosynthesis. Additionally, SCPs diminished formation of reactive oxygen species, thereby preventing damage within Photosystem II. We conclude that the lack of SCP-function to remove free chlorophyll under stress conditions has a large impact on the metabolism of the entire cell.
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| 6. |
- Tibiletti, Tania, 1984-
(författare)
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Functional studies on the Light-harvesting-Like (LiL) Proteins in Cyanobacteria and Cryptophytes
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The light-harvesting like (LiL) proteins are a widely spread group of proteins within photosynthetic organisms. They are membrane proteins composed of one to four transmembrane helices and – in homology to the light-harvesting complexes of algae and higher plants – at least one of these transmembrane helices contains the chlorophyll a/b-binding (CAB) domain. Opposite to the light-harvesting antenna complexes, LiL proteins are stress induced and they have been shown to be involved in protection of the photosynthetic apparatus. The work presented in this thesis is focused on understanding the function of one-helical LiL proteins of the cryptophyte algae Guillardia theta and the cyanobacterium Synechocystis sp. PCC 6803. G. theta contains two genes encoding LiL proteins, one is localized in the plastid (hlipP), the other in the nucleomorph (HlipNm). Both genes are expressed in normal growth condition, but they are not induced by high light. Immunostaining indicated that HlipNm is translated, but not light-induced. These proteins therefore seem not to be involved in photoprotective mechanisms of G. theta. In the cyanobacterium Synechocystis sp. PCC 6803 four one-helical LiL proteins were identified, they are called Small CAB-like Proteins (SCPs); a fifth LiL (ScpA) is fused with the ferrochelatase (FC), an enzyme involved in the heme synthesis. Our analysis revealed that SCPs are involved in the de novo assembly/repair cycle of Photosystem II, stabilizing the chlorophyll pigments at their protein scaffold. The in vitro characterization of the recombinant FC showed that ScpA is involved in the product-release of the catalytic domain of the enzyme, thereby regulating substrate availability for chlorophyll- or heme- biosynthesis. Finally, using a transcriptomic and metabolomic approaches, I was able to show that deletion of all SCP genes has profound impact on the cell organization and metabolism. In SCP-depleted cells, production of reactive oxygen species (ROS) is increased, while the amount of Photosystem II per cell volume is decreased, causing a macronutrient-deficient phenotype. Therefore, SCPs are important for stress protection and help to maintain a metabolic equilibrium within the cell.
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| 7. |
- Tibiletti, Tania, 1984-, et al.
(författare)
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The small CAB-like proteins of the cyanobacterium Synechocystis sp. PCC 6803 : Transcriptomic, proteomic and metabolomic analyses reveal new insights into their function
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The five small CAB-like proteins (ScpA-E) of the cyanobacterium Synechocystis sp. PCC 6803 consist of one transmembrane helix and belong to the light-harvesting like family. While in wild type they are induced by various stresses, in cells with Photosystem I (PSI) -less background the SCPs are constitutively expressed. Here we performed a detailed comparison of a PSI-less control strain with a strain depleted of PSI and all SCPs, with the aim to elucidate the function of the SCPs within Photosystem II. Electron microscopical immages showed a drastic alteration of the cellular organization, visible by a rough surface and few thylakoid membranes in the PSI-less/ScpABCDE- strain. Immunoblots pointed to a decreased amount of PSII per cell volume. Deletion of the scp genes also affected the carbon- and nitrogen-balance and thereby the carbohydrate accumulation at the expenses of protein- and chlorophyll-synthesis as judged by transcriptomic and metabolomic analyses. Our results show that SCPs ensure a correct assembly/repair of PSII and therefore are important for the adaptation to environmental stresses - especially during the generation of reactive oxygen species.
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| 8. |
- Tibiletti, Tania, et al.
(författare)
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The stress-induced SCP/HLIP family of small light-harvesting-like proteins (ScpABCDE) protects Photosystem II from photoinhibitory damages in the cyanobacterium Synechocystis sp. PCC 6803
- 2018
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Ingår i: Photosynthesis Research. - : Springer. - 0166-8595 .- 1573-5079. ; 135:1–3, s. 103-114
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Tidskriftsartikel (refereegranskat)abstract
- Small CAB-like proteins (SCPs) are single-helix light-harvesting-like proteins found in all organisms performing oxygenic photosynthesis. We investigated the effect of growth in moderate salt stress on these stress-induced proteins in the cyanobacterium Synechocystis sp. PCC 6803 depleted of Photosystem I (PSI), which expresses SCPs constitutively, and compared these cells with a PSI-less/ScpABCDE− mutant. SCPs, by stabilizing chlorophyll-binding proteins and Photosystem II (PSII) assembly, protect PSII from photoinhibitory damages, and in their absence electrons accumulate and will lead to ROS formation. The presence of 0.2 M NaCl in the growth medium increased the respiratory activity and other PSII electron sinks in the PSI-less/ScpABCDE− strain. We postulate that this salt-induced effect consumes the excess of PSII-generated electrons, reduces the pressure of the electron transport chain, and thereby prevents 1O2 production.
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