Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme.
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.
Department of Photochemistry and Molecular Science, Angström laboratory, Uppsala University, P.O. Box 523, SE-75120 Uppsala, Sweden.
Tanai
T
Cardona
Natalia
N
Battchikova
Pengpeng
P
Zhang
Karin
K
Stensjö
Eva-Mari
EM
Aro
Peter
P
Lindblad
Ann
A
Magnuson
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D015153:Blotting, Western; D002473:Cell Wall / Q000378:metabolism; D045347:Cytochromes b6 / Q000378:metabolism; D045348:Cytochromes f / Q000378:metabolism; D004579:Electron Transport; D015180:Electrophoresis, Gel, Two-Dimensional; D007425:Intracellular Membranes / Q000378:metabolism; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D046937:Nostoc / Q000201:enzymology / Q000378:metabolism*; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011808:Quinone Reductases / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D020524:Thylakoids / Q000201:enzymology / Q000378:metabolism*
D001426:Bacterial Proteins; D045347:Cytochromes b6; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D045348:Cytochromes f; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases; D006180:Proton-Translocating ATPases; D012273:Ribulose-Bisphosphate Carboxylase