| 1. |
- Cardol, Pierre, et al.
(författare)
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Oxidative Phosphorylation : Building blocks and related components
- 2009
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Ingår i: The Chlamydomonas Sourcebook. - Oxford : Academic Press. - 0123708753 ; , s. 469-502
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter summarizes the knowledge of the oxidative phosphorylation (OXPHOS) constituents of Chlamydomonas and of the components involved in their biogenesis and addresses alternate dehydrogenases and oxidases which are particular to photosynthetic organisms, and several other mitochondrial components related to OXPHOS. Reference to the components of Polytomella sp., a colorless alga closely related to Chlamydomonas is clearly made. The main complexes involved in electron transport seem to share a similar number of subunits, and many of the algal polypeptides have plant homologues. Some differences are apparent, such as the presence of a fragmented COX2 subunit, which seems to be unique to chlorophyte algae. OXPHOS is defined as an electron transfer chain driven by substrate oxidation that is coupled to the synthesis of ATP through an electrochemical transmembrane gradient. The characterization of Arabidopsis mitochondrial components through proteomic approaches has advanced significantly. As a unicellular organism, Chlamydomonas offers the unique opportunity to study organelle-organelle interactions, particularly between mitochondria and chloroplasts. It has become evident that crosstalk between these organelles takes place, mainly through intracellular metabolite pools. © 2009 Elsevier Inc. All rights reserved.
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| 2. |
- Eriksson, Martin, 1970, et al.
(författare)
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Community-Level Analysis of psbA Gene Sequences and Irgarol Tolerance in Marine Periphyton
- 2009
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Ingår i: Applied and Environmental Microbiology. - Washington, D.C. : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 75:4, s. 897-906
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Tidskriftsartikel (refereegranskat)abstract
- This study analyzes psbA gene sequences, predicted D1 protein sequences, species relative abundance, and pollution-induced community tolerance in marine periphyton communities exposed to the antifouling compound Irgarol 1051. The mechanism of action of Irgarol is the inhibition of photosynthetic electron transport at photosystem II by binding to the D1 protein. The metagenome of the communities was used to produce clone libraries containing fragments of the psbA gene encoding the D1 protein. Community tolerance was quantified with a short-term test for the inhibition of photosynthesis. The communities were established in a continuous flow of natural seawater through microcosms with or without added Irgarol. The selection pressure from Irgarol resulted in an altered species composition and an inducted community tolerance to Irgarol. Moreover, there was a very high diversity in the psbA gene sequences in the periphyton, and the composition of psbA and D1 fragments within the communities was dramatically altered by increased Irgarol exposure. Even though tolerance to this type of compound in land plants often depends on a single amino acid substitution (Ser(264)-> Gly) in the D1 protein, this was not the case for marine periphyton species. Instead, the tolerance mechanism likely involves increased degradation of D1. When we compared sequences from low and high Irgarol exposure, differences in nonconserved amino acids were found only in the so-called PEST region of D1, which is involved in regulating its degradation. Our results suggest that environmental contamination with Irgarol has led to selection for high-turnover D1 proteins in marine periphyton communities at the west coast of Sweden.
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| 3. |
- Farkas, Daniel, et al.
(författare)
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Cloning, expression and purification of the luminal domain of spinach photosystem 1 subunit PsaF functional in binding to plastocyanin and with a disulfide bridge required for folding
- 2011
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Ingår i: Protein Expression and Purification. - San Diego : Academic Press. - 1046-5928 .- 1096-0279. ; 78:2, s. 156-166
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Tidskriftsartikel (refereegranskat)abstract
- The photosystem 1 subunit PsaF is involved in the docking of the electron-donor proteins plastocyanin and cytochrome c6 in eukaryotic photosynthetic organisms. Here we report the expression, purification and basic characterization of the luminal domain of spinach PsaF, encompassing amino-acid residues 1-79. The recombinant protein was expressed in Escherichia coli BL21 (DE3) using a pET32 Xa/LIC thioredoxin fusion system. The thioredoxin fusion protein contained a His6 tag and was removed and separated from PsaF through proteolytic digestion by factor Xa followed by immobilized metal affinity chromatography. Further purification with size-exclusion chromatography resulted in a final yield of approximately 6 mg PsaF from one liter growth medium. The correct identity after the factor Xa treatment of PsaF was verified by FT-ICR mass spectrometry which also showed that the purified protein contains an intact disulfide bridge between Cys residues 6 and 38. Secondary structure and folding was further explored using far-UV CD spectroscopy indicating a α-helical content in agreement with the 3.3 Å-resolution crystal structure of photosystem I Ref. [5] and a helix-coil transition temperature of 29 °C. Thermofluorescence studies showed that the disulfide bridge is necessary to keep the overall fold of the protein and that hydrophobic regions become exposed at 50-65 °C depending on the ionic strength. The described expression and purification procedure can be used for isotopic labeling of the protein and 15N-HSQC NMR studies indicated a slow or intermediate exchange between different conformations of the prepared protein and that it belongs to the molten-globule structural family. Finally, by using a carboxyl- and amine-reactive zero-length crosslinker, we have shown that the recombinant protein binds to plastocyanin by a specific, native-like, electrostatic interaction, hence, confirming its functionality.
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| 4. |
- Figueroa-Martinez, Francisco, et al.
(författare)
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Reconstructing the mitochondrial protein import machinery of Chlamydomonas reinhardtii
- 2008
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Ingår i: Genetics. - Austin, Tex. : The Genetics Society. - 0016-6731 .- 1943-2631. ; 179:1, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- In Chlamydomonas reinhardtii several nucleus-encoded proteins that participate in the mitochondrial oxidative phosphorylation are targeted to the organelle by unusually long mitochondrial targeting sequences. Here, we explored the components of the mitochondrial import machinery of the green alga. We mined the algal genome, searching for yeast and plant homologs, and reconstructed the mitochondrial import machinery. All the main translocation components were identified in Chlamydomonas as well as in Arabidopsis thaliana and in the recently sequenced moss Physcomitrella patens. Some of these components appear to be duplicated, as is the case of Tim22. In contrast, several yeast components that have relatively large hydrophilic regions exposed to the cytosol or to the intermembrane space seem to be absent in land plants and green algae. If present at all, these components of plants and algae may differ significantly from their yeast counterparts. We propose that long mitochondrial targeting sequences in some Chlamydomonas mitochondrial protein precursors are involved in preventing the aggregation of the hydrophobic proteins they carry.
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| 5. |
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| 6. |
- Funes, Soledad, et al.
(författare)
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Chlamydomonas reinhardtii : the model of choice to study mitochondria from unicellular photosynthetic organisms.
- 2007
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Ingår i: Methods in Molecular Biology. - Clifton, NJ : Humana Press. - 1064-3745. - 9781588296672 - 9781597453653 ; 372, s. 137-149
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Chlamydomonas reinhardtii is a model organism to study photosynthesis, cellular division, flagellar biogenesis, and, more recently, mitochondrial function. It has distinct advantages in comparison to higher plants because it is unicellular, haploid, and amenable to tetrad analysis, and its three genomes are subject to specific transformation. It also has the possibility to grow either photoautotrophically or heterotrophically on acetate, making the assembly of the photosynthetic machinery not essential for cell viability. Methods developed allow the isolation of C. reinhardtii mitochondria free of thylakoid contaminants. We review the general procedures used for the biochemical characterization of mitochondria from this green alga.
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| 7. |
- Liess, Antonia, 1975-, et al.
(författare)
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Ecosystem consequences of boreal lake browning and eutrophication – using mesocoms as tools for food web studies
- 2022
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Ingår i: Abstract Book. ; , s. 111-111
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- With increasing temperatures and precipitation, as well as land use changes in boreal regions, waterbodies are receiving larger inputs of coloured terrestrial humic substances. At the same time, nutrient inputs are increasing. This brownificationin combination with increasing nutrient levels has consequences for the aquatic food web in terms of species composition and energy transfer efficiency. In Lake Bolmen, Sweden’s 7ths largest lake, brownification additionally creates problems for drinkingwater production, since this lake is an important drinking water reservoir of southern Sweden. Lake monitoring data show a clear pattern of increasing brownification in Lake Bolmen over the preceding decades. To understand the consequences ofincreased browning and of increased nutrient inputs for Lake Bolmen’s food web on bacterial production, and phytoplankton and zooplankton species community composition and abundance, we conducted a 6-week mesocosm experiment during summer 2021. Brownification and nutrient ratios were manipulated. Measures of algal pigment concentrations show that browning has strong effects on algal pigment composition and thus probably on algal taxonomic composition. Our results suggest that brownification affects basic producer community composition in lakes, thus possibly changing community composition and biomass of higher trophic levels of the aquatic food web in boreal regions.
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