|Entry||Database: EMDB / ID: EMD-9877|
|Title||Structure of PSI dimer from Anabaena|
|Biological species||Nostoc sp. PCC 7120 (Cyanobacteria)|
|Method||single particle reconstruction / cryo EM / Resolution: 4 Å|
|Authors||Kato K / Nagao R / Shen JR / Miyazaki N / Akita F|
|Citation||Journal: Nat Commun / Year: 2019|
Title: Structure of a cyanobacterial photosystem I tetramer revealed by cryo-electron microscopy.
Authors: Koji Kato / Ryo Nagao / Tian-Yi Jiang / Yoshifumi Ueno / Makio Yokono / Siu Kit Chan / Mai Watanabe / Masahiko Ikeuchi / Jian-Ren Shen / Seiji Akimoto / Naoyuki Miyazaki / Fusamichi Akita /
Abstract: Photosystem I (PSI) functions to harvest light energy for conversion into chemical energy. The organisation of PSI is variable depending on the species of organism. Here we report the structure of a ...Photosystem I (PSI) functions to harvest light energy for conversion into chemical energy. The organisation of PSI is variable depending on the species of organism. Here we report the structure of a tetrameric PSI core isolated from a cyanobacterium, Anabaena sp. PCC 7120, analysed by single-particle cryo-electron microscopy (cryo-EM) at 3.3 Å resolution. The PSI tetramer has a C2 symmetry and is organised in a dimer of dimers form. The structure reveals interactions at the dimer-dimer interface and the existence of characteristic pigment orientations and inter-pigment distances within the dimer units that are important for unique excitation energy transfer. In particular, characteristic residues of PsaL are identified to be responsible for the formation of the tetramer. Time-resolved fluorescence analyses showed that the PSI tetramer has an enhanced excitation-energy quenching. These structural and spectroscopic findings provide insights into the physiological significance of the PSI tetramer and evolutionary changes of the PSI organisations.
|Structure viewer||EM map: |
Downloads & links
|File||Download / File: emd_9877.map.gz / Format: CCP4 / Size: 325 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)|
|Projections & slices|
Images are generated by Spider.
|Voxel size||X=Y=Z: 1.12 Å|
|Symmetry||Space group: 1|
CCP4 map header:
-Entire PSI dimer
|Entire||Name: PSI dimer / Number of components: 1|
-Component #1: protein, PSI dimer
|Protein||Name: PSI dimer / Recombinant expression: No|
|Mass||Theoretical: 700 kDa|
|Source||Species: Nostoc sp. PCC 7120 (Cyanobacteria)|
|Specimen||Specimen state: Particle / Method: cryo EM|
|Sample solution||Specimen conc.: 0.014 mg/mL / pH: 6.5|
|Vitrification||Instrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Temperature: 277 K / Humidity: 100 %|
-Electron microscopy imaging
Model: Titan Krios / Image courtesy: FEI Company
|Imaging||Microscope: FEI TITAN KRIOS|
|Electron gun||Electron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Electron dose: 40 e/Å2 / Illumination mode: FLOOD BEAM|
|Lens||Imaging mode: BRIGHT FIELD|
|Specimen Holder||Model: OTHER|
|Camera||Detector: FEI FALCON III (4k x 4k)|
|Processing||Method: single particle reconstruction / Applied symmetry: C1 (asymmetric) / Number of projections: 117137|
|3D reconstruction||Software: RELION / Resolution: 4 Å / Resolution method: FSC 0.143 CUT-OFF|
|FSC plot (resolution estimation)|
-Atomic model buiding
|Modeling #1||Refinement protocol: flexible / Target criteria: Correlation coefficient / Refinement space: REAL|
Input PDB model: 1JB0
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