Journal: Cell / Year: 2017 Title: Cryo-EM Structure of a KCNQ1/CaM Complex Reveals Insights into Congenital Long QT Syndrome. Authors: Ji Sun / Roderick MacKinnon / Abstract: KCNQ1 is the pore-forming subunit of cardiac slow-delayed rectifier potassium (I) channels. Mutations in the kcnq1 gene are the leading cause of congenital long QT syndrome (LQTS). Here, we present ...KCNQ1 is the pore-forming subunit of cardiac slow-delayed rectifier potassium (I) channels. Mutations in the kcnq1 gene are the leading cause of congenital long QT syndrome (LQTS). Here, we present the cryoelectron microscopy (cryo-EM) structure of a KCNQ1/calmodulin (CaM) complex. The conformation corresponds to an "uncoupled," PIP-free state of KCNQ1, with activated voltage sensors and a closed pore. Unique structural features within the S4-S5 linker permit uncoupling of the voltage sensor from the pore in the absence of PIP. CaM contacts the KCNQ1 voltage sensor through a specific interface involving a residue on CaM that is mutated in a form of inherited LQTS. Using an electrophysiological assay, we find that this mutation on CaM shifts the KCNQ1 voltage-activation curve. This study describes one physiological form of KCNQ1, depolarized voltage sensors with a closed pore in the absence of PIP, and reveals a regulatory interaction between CaM and KCNQ1 that may explain CaM-mediated LQTS.
History
Deposition
Apr 28, 2017
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Header (metadata) release
May 24, 2017
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Map release
Jun 7, 2017
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Update
Mar 13, 2024
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Current status
Mar 13, 2024
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Name: CALCIUM ION / type: ligand / ID: 3 / Number of copies: 3 / Formula: CA
Molecular weight
Theoretical: 40.078 Da
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Experimental details
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Structure determination
Method
cryo EM
Processing
single particle reconstruction
Aggregation state
particle
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Sample preparation
Concentration
5 mg/mL
Buffer
pH: 7.2
Vitrification
Cryogen name: ETHANE / Chamber temperature: 298 K / Instrument: FEI VITROBOT MARK IV / Details: 90-100% humidity.
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Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
Film or detector model: DIRECT ELECTRON DE-64 (8k x 8k) / Detector mode: SUPER-RESOLUTION / Average electron dose: 1.78 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron optics
Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
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Image processing
Startup model
Type of model: OTHER / Details: Generated from 2D class average using EMAN
Final reconstruction
Applied symmetry - Point group: C4 (4 fold cyclic) / Resolution.type: BY AUTHOR / Resolution: 3.7 Å / Resolution method: FSC 0.143 CUT-OFF / Software: (Name: RELION (ver. 1.3), FREALIGN (ver. 9.03)) Details: Entry was refined using space group P4 and cell parameters a=b=c=332.8 and alpha=beta=gamma=90. Number images used: 69415
Initial angle assignment
Type: PROJECTION MATCHING
Final angle assignment
Type: ANGULAR RECONSTITUTION
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