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2. Interaction of photosystem 2-LHC2 supercomplexes in adjacent layers of stacked chloroplast thylakoid membranes

Creator:
Bumba, L., Hušák, M., and Vácha, F.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
electron microscopy, membrane proteins, model, photosynthesis, photosystem 2, Pisum, and single particle image analysis
Language:
Multiple languages
Description:
Two types of photosystem 2-light-harvesting complex 2 (PS2-LHC2) supercomplexes with similar pigment and protein composition were isolated directly from thylakoid membranes by sucrose density gradient centrifugation. Electron microscopy and single particle image analysis revealed the first Type as single unpaired PS2-LHC2 supercomplexes, whereas the second Type was characterized as pairs of two PS2-LHC2 supercomplexes attached together by their stromal sides. Unstacking of thylakoid membranes resulted in a spontaneous disintegration of the paired supercomplexes into single unpaired particles. A model of the organisation of the pigment-protein complexes in grana region is proposed. and L. Bumba, M. Hušák, F. Vácha.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Isolation and characterization of an oxygen evolving photosystem 2 core complex from the thermophilic cyanobacterium Mastigocladus laminosus

Creator:
Ramesh, V. M., Fish, A., Michaeli, D., Keren, N., Ohad, I., Vorchovsky, L., and Nechushtai, R.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
2,6-dimethylbenzoquinone, fluorescence, membrane proteins, oxygen evolution rate, reaction center, and thermoluminescence
Language:
Multiple languages
Description:
A novel purification procedure was developed for the isolation of oxygen evolving photosystem 2 (PS2) from Mastigocladus laminosus. The isolation procedure involves dodecyl maltoside extraction followed by column chromatography using anion exchange resins. The isolated PS2 reaction center (RC) was analyzed for its biochemical and biophysical characteristics. Analysis by SDS polyacrylamide gel electrophoresis revealed that the complex contained five intrinsic membrane proteins (CP 47, CP 43, D1, D2, and cyt b559) and at least three low molecular mass proteins. The complex exhibited high rates of oxygen evolution [333 mmol(O2) kg-1(Chl) s-1] in the presence of 2.5 mM 2,6-dimethylbenzoquinone (DMBQ) as an artificial electron acceptor. The red chlorophyll a absorption peak of this complex was observed at 673.5±0.2 nm. The isolated PS2 core complex was free of photosystem 1 as inferred from its SDS-PAGE and fluorescence spectrum. The electron transfer properties of the Mastigocladus cells and the purified PS2 core complex were further probed by measuring thermoluminescence signals, which indicated the presence of a primary quinone electron acceptor (QA) in the purified PS2 core complex. and V. M. Ramesh ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public