|Entry||Database: EMDB / ID: EMD-0539|
|Title||Averaged structure of Photosystem II holocomplex on thylakoid membrane from diatom|
|Sample||Thylakoid membrane purified from diatom|
|Biological species||Phaeodactylum tricornutum (eukaryote)|
|Method||subtomogram averaging / cryo EM / Resolution: 26 Å|
|Authors||Chen M / Kuang X / Levitan O / Falkowski P / Dai W|
|Funding support|| United States, 3 items |
|Citation||Journal: Proc. Natl. Acad. Sci. U.S.A. / Year: 2019|
Title: Structural and functional analyses of photosystem II in the marine diatom .
Authors: Orly Levitan / Muyuan Chen / Xuyuan Kuang / Kuan Yu Cheong / Jennifer Jiang / Melissa Banal / Nikhita Nambiar / Maxim Y Gorbunov / Steven J Ludtke / Paul G Falkowski / Wei Dai /
Abstract: A descendant of the red algal lineage, diatoms are unicellular eukaryotic algae characterized by thylakoid membranes that lack the spatial differentiation of stroma and grana stacks found in green ...A descendant of the red algal lineage, diatoms are unicellular eukaryotic algae characterized by thylakoid membranes that lack the spatial differentiation of stroma and grana stacks found in green algae and higher plants. While the photophysiology of diatoms has been studied extensively, very little is known about the spatial organization of the multimeric photosynthetic protein complexes within their thylakoid membranes. Here, using cryo-electron tomography, proteomics, and biophysical analyses, we elucidate the macromolecular composition, architecture, and spatial distribution of photosystem II complexes in diatom thylakoid membranes. Structural analyses reveal 2 distinct photosystem II populations: loose clusters of complexes associated with antenna proteins and compact 2D crystalline arrays of dimeric cores. Biophysical measurements reveal only 1 photosystem II functional absorption cross section, suggesting that only the former population is photosynthetically active. The tomographic data indicate that the arrays of photosystem II cores are physically separated from those associated with antenna proteins. We hypothesize that the islands of photosystem cores are repair stations, where photodamaged proteins can be replaced. Our results strongly imply convergent evolution between the red and the green photosynthetic lineages toward spatial segregation of dynamic, functional microdomains of photosystem II supercomplexes.
|Structure viewer||EM map: |
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|File||Download / File: emd_0539.map.gz / Format: CCP4 / Size: 8 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)|
|Projections & slices|
Images are generated by Spider.
|Voxel size||X=Y=Z: 3.49 Å|
|Symmetry||Space group: 1|
CCP4 map header:
-Entire Thylakoid membrane purified from diatom
|Entire||Name: Thylakoid membrane purified from diatom / Number of components: 1|
-Component #1: cellular-component, Thylakoid membrane purified from diatom
|Cellular-component||Name: Thylakoid membrane purified from diatom / Recombinant expression: No|
|Source||Species: Phaeodactylum tricornutum (eukaryote)|
|Source (natural)||Organelle: Thylakoid membrane|
|Specimen||Specimen state: Cell / Method: cryo EM|
|Sample solution||pH: 7.5|
|Vitrification||Instrument: LEICA EM GP / Cryogen name: ETHANE / Humidity: 100 %|
-Electron microscopy imaging
Model: Talos Arctica / Image courtesy: FEI Company
|Imaging||Microscope: FEI TALOS ARCTICA|
|Electron gun||Electron source: FIELD EMISSION GUN / Accelerating voltage: 200 kV / Electron dose: 2 e/Å2 / Illumination mode: FLOOD BEAM|
|Lens||Imaging mode: BRIGHT FIELD|
|Specimen Holder||Model: OTHER|
|Camera||Detector: GATAN K2 BASE (4k x 4k)|
-Atomic model buiding
|Modeling #1||Refinement protocol: rigid body / Target criteria: correlation coefficient / Refinement space: REAL|
Input PDB model: 4YUU
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