Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme |
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Authors: | Tanai Cardona Pengpeng Zhang Eva-Mari Aro Ann Magnuson |
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Institution: | a Department of Photochemistry and Molecular Science, Ångström laboratory, Uppsala University, P.O. Box 523, SE-75120 Uppsala, Sweden b Plant Physiology and Molecular Biology, Department of Biology, University of Turku, FIN-20014 Turku, Finland |
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Abstract: | 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 a significant 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 Photosystem II 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. |
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Keywords: | ATP adenosine triphosphate BN blue native Chl chlorophyll CLSM confocal laser scanning microscopy DM d-maltoside" target="_blank">n-dodecyl β-d-maltoside DBMIB dibromothymoquinone DCBQ 2 6-dichloro-p-benzoquinone DCMU 3-(3 4-dichlorophenyl)-1 1-dimethylurea DCPIP 2 6-dichlorophenolindophenol DPC diphenylcarbazide EDTA ethylene diamine tetraacetic acid ESI electrospray ionization FNR ferredoxin:NADP+ reductase Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid Mes 4-morpholinoethane-sulfonic acid MS mass spectrometry NDH-1 NAD(P)H dehydrogenase PAGE polyacrylamide gel electrophoresis PPBQ phenyl-p-benzoquinone PSI Photosystem I PSII Photosystem II Rubisco Ribulose-1 5-bisphosphate carboxylase/oxygenase SDS sodium dodecyl sulfate Tris tris(hydroxymethyl)aminomethane TOF time of flight |
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