Gating movements and ion permeation in HCN4 pacemaker channels.
Mol Cell
; 81(14): 2929-2943.e6, 2021 07 15.
Article
in En
| MEDLINE
| ID: mdl-34166608
ABSTRACT
The HCN1-4 channel family is responsible for the hyperpolarization-activated cation current If/Ih that controls automaticity in cardiac and neuronal pacemaker cells. We present cryoelectron microscopy (cryo-EM) structures of HCN4 in the presence or absence of bound cAMP, displaying the pore domain in closed and open conformations. Analysis of cAMP-bound and -unbound structures sheds light on how ligand-induced transitions in the channel cytosolic portion mediate the effect of cAMP on channel gating and highlights the regulatory role of a Mg2+ coordination site formed between the C-linker and the S4-S5 linker. Comparison of open/closed pore states shows that the cytosolic gate opens through concerted movements of the S5 and S6 transmembrane helices. Furthermore, in combination with molecular dynamics analyses, the open pore structures provide insights into the mechanisms of K+/Na+ permeation. Our results contribute mechanistic understanding on HCN channel gating, cyclic nucleotide-dependent modulation, and ion permeation.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Potassium Channels
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Ion Channel Gating
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Cell Membrane Permeability
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Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
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Ions
/
Muscle Proteins
Limits:
Humans
Language:
En
Journal:
Mol Cell
Journal subject:
BIOLOGIA MOLECULAR
Year:
2021
Document type:
Article
Affiliation country:
Italy
Publication country:
EEUU
/
ESTADOS UNIDOS
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ESTADOS UNIDOS DA AMERICA
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EUA
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UNITED STATES
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UNITED STATES OF AMERICA
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US
/
USA