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Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Department of Biology, University of Turku. (Laboratory of Plant Physiology and Molecular Biology)
Department of Biology, University of Turku. (Laboratory of Plant Physiology and Molecular Biology)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
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2009 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1787, no 4, 252-263 p.Article in journal (Refereed) Published
Abstract [en]

Filamentous, heterocystous cyanobacteria are capable of nitrogen fixation and photoautotrophic growth. Nitrogen fixation takes place in heterocysts that differentiate as a result of nitrogen starvation. Heterocysts uphold a microoxic environment to avoid inactivation of nitrogenase, e.g. by downregulation of oxygenic photosynthesis. The ATP and reductant requirement for the nitrogenase reaction is considered to depend on Photosystem I, but little is known about the organization of energy converting membrane proteins in heterocysts. We have investigated the membrane proteome of heterocysts from nitrogen fixing filaments of Nostoc punctiforme sp. PCC 73102, by 2D gel electrophoresis and mass spectrometry. The membrane proteome was found to be dominated by the Photosystem I and ATP-synthase complexes.We could identify asignificant amount of assembled Photosystem II complexes containing the D1, D2, CP43, CP47 and PsbO proteins from these complexes. We could also measure light-driven in vitro electron transfer from Photosystem II in heterocyst thylakoid membranes. We did not find any partially disassembled PhotosystemII complexes lacking the CP43 protein. Several subunits of the NDH-1 complex were also identified. The relative amount of NDH-1M complexes was found to be higher than NDH-1L complexes, which might suggest a role for this complex in cyclic electron transfer in the heterocysts of Nostoc punctiforme.

Place, publisher, year, edition, pages
Elsevier , 2009. Vol. 1787, no 4, 252-263 p.
Keyword [en]
Cyanobacteria, Nostoc, Heterocyst, Photosystem II, Fluorescence, BN-PAGE
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:uu:diva-108433DOI: 10.1016/j.bbabio.2009.01.015ISI: 000264575700005OAI: oai:DiVA.org:uu-108433DiVA: diva2:235945
Available from: 2012-05-08 Created: 2009-09-18 Last updated: 2016-04-21
In thesis
1. The Heterocysts of Nostoc punctiforme: From Proteomics to Energy Transfer
Open this publication in new window or tab >>The Heterocysts of Nostoc punctiforme: From Proteomics to Energy Transfer
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis is to provide a thorough characterization of the photosynthetic machinery from the heterocysts of Nostoc punctiforme strain ATCC 29133. In this thesis I describe the protocols I have optimized for the isolation of thylakoids from vegetative cells, the purification of heterocysts and the isolation of thylakoids from the purified heterocysts. The composition of the thylakoid membranes was studied by two dimensional electrophoresis and mass-spectrometry. Further insight into the functionality of the photosynthetic complexes was obtained by EPR, electron transport measurements through Photosystem II (PSII), and fluorescence spectroscopy. The proteome of the heterocysts thylakoids compared to that of the vegetative cell was found to be dominated by Photosystem I (PSI) and ATP-synthase complexes, both essential for keeping high nitrogenase activities. Surprisingly, we found a significant amount of assembled monomeric PSII complexes in the heterocysts thylakoid membranes. We measured in vitro light-driven electron transfer from PSII in heterocysts using an artificial electron donor, suggesting that under certain circumstances heterocysts might activate PSII. Parallel to my main research I also worked in a collaboration to elucidate the total proteome of Nostoc sp. strain 7120 and Nostoc punctiforme using quantitative shotgun proteomics. Several hundred proteins were quantified for both species. It was possible to trace the detailed changes that occurred in the energy and nitrogen metabolism of a heterocyst after differentiation. Moreover, the presence of PSII proteins identified in our membrane proteome was also confirmed and extended. Lastly, I studied how the heterocysts are capable of responding to variations in light quality as compared to vegetative cells. Using 77 K fluorescence spectroscopy on heterocysts and vegetative cells previously illuminated with light at specific wavelengths, I was able to demonstrate that heterocysts still possess a possibly modified but functional antenna system, capable of harvesting light and transferring energy preferentially to PSI. The characterization of the membrane and total proteome permitted to draw a more comprehensive and integrated picture of the interplay between the distinct metabolic processes that are carried out in each cell type at the same time; from oxygenic photosynthesis and carbon fixation in the vegetative cells to the anoxygenic cyclic photophosphorylation essential to power nitrogen assimilation in the heterocysts.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 78 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 671
Keyword
Nostoc punctiforme, heterocyst, photosynthesis, thylakoid, isolation, proteomics, photosystem, energy transfer, hydrogen
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:uu:diva-108413 (URN)978-91-554-7607-6 (ISBN)
Public defence
2009-10-30, Häggsalen, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-10-09 Created: 2009-09-17 Last updated: 2009-10-09

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Cardona, TanaiStensjö, KarinLindblad, PeterMagnuson, Ann

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