|Entry||Database: EMDB / ID: 0102|
|Title||symmetric structure of tPDE6|
|Sample||truncated, active dimeric complex of PDE6 containing alpha and beta subunits, but no gamma subunitTruncation (disambiguation):|
|Source||Bos taurus (cattle)|
|Method||single particle reconstruction / cryo EM / 28 Å resolution|
|Authors||Qureshi BM / Behrmann E / Loerke J / Spahn CMT / Heck M|
|Citation||Journal: Open Biol / Year: 2018|
Title: It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods.
Authors: Bilal M Qureshi / Elmar Behrmann / Johannes Schöneberg / Justus Loerke / Jörg Bürger / Thorsten Mielke / Jan Giesebrecht / Frank Noé / Trevor D Lamb / Klaus Peter Hofmann / Christian M T Spahn / Martin Heck
Abstract: Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and ...Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein α-subunits (Gα*). To investigate the activation mechanism of mammalian rod PDE6, we have collected functional and structural data, and analysed them by reaction-diffusion simulations. Gα* titration of membrane-bound PDE6 reveals a strong functional asymmetry of the enzyme with respect to the affinity of Gα* for its two binding sites on membrane-bound PDE6 and the enzymatic activity of the intermediary 1 : 1 Gα* · PDE6 complex. Employing cGMP and its 8-bromo analogue as substrates, we find that Gα* · PDE6 forms with high affinity but has virtually no cGMP hydrolytic activity. To fully activate PDE6, it takes a second copy of Gα* which binds with lower affinity, forming Gα* · PDE6 · Gα*. Reaction-diffusion simulations show that the functional asymmetry of membrane-bound PDE6 constitutes a coincidence switch and explains the lack of G protein-related noise in visual signal transduction. The high local concentration of Gα* generated by a light-activated rhodopsin molecule efficiently activates PDE6, whereas the low density of spontaneously activated Gα* fails to activate the effector enzyme.
|Date||Deposition: Jul 5, 2018 / Header (metadata) release: Aug 22, 2018 / Map release: Sep 5, 2018 / Last update: Sep 5, 2018|
|Structure viewer||EM map: |
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|File||emd_0102.map.gz (map file in CCP4 format, 1049 KB)|
|Projections & slices|
Images are generated by Spider.
|Voxel size||X=Y=Z: 5.2 Å|
CCP4 map header:
-Entire truncated, active dimeric complex of PDE6 containing alpha and be...
|Entire||Name: truncated, active dimeric complex of PDE6 containing alpha and beta subunits, but no gamma subunit|
Number of components: 1
-Component #1: protein, truncated, active dimeric complex of PDE6 containing alp...
|Protein||Name: truncated, active dimeric complex of PDE6 containing alpha and beta subunits, but no gamma subunitTruncation (disambiguation)|
Recombinant expression: No
|Mass||Experimental: 200 kDa|
|Source||Species: Bos taurus (cattle)|
|Specimen||Specimen state: particle / Method: cryo EM|
|Sample solution||pH: 7.5|
|Vitrification||Cryogen name: ETHANE|
-Electron microscopy imaging
Model: Tecnai Spirit / Image courtesy: FEI Company
|Imaging||Microscope: FEI TECNAI SPIRIT|
|Electron gun||Electron source: LAB6 / Accelerating voltage: 120 kV / Electron dose: 2 e/Å2 / Illumination mode: FLOOD BEAM|
|Lens||Imaging mode: BRIGHT FIELD|
|Specimen Holder||Model: OTHER|
|Camera||Detector: FEI EAGLE (2k x 2k)|
|Processing||Method: single particle reconstruction / Applied symmetry: C2 (2 fold cyclic) / Number of projections: 19716|
|3D reconstruction||Resolution: 28 Å / Resolution method: FSC 0.5 CUT-OFF|
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