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- PDB-6cnm: Cryo-EM structure of the human SK4/calmodulin channel complex -

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Basic information

Entry
Database: PDB / ID: 6cnm
TitleCryo-EM structure of the human SK4/calmodulin channel complex
Components
  • Calmodulin-1
  • Intermediate conductance calcium-activated potassium channel protein 4
KeywordsMEMBRANE PROTEIN / ion channel / neuroscience / calmodulin
Function / homology
Function and homology information


intermediate conductance calcium-activated potassium channel activity / small conductance calcium-activated potassium channel activity / saliva secretion / Ca2+ activated K+ channels / calcium-activated potassium channel activity / stabilization of membrane potential / positive regulation of potassium ion transmembrane transport / cell volume homeostasis / CaM pathway / Cam-PDE 1 activation ...intermediate conductance calcium-activated potassium channel activity / small conductance calcium-activated potassium channel activity / saliva secretion / Ca2+ activated K+ channels / calcium-activated potassium channel activity / stabilization of membrane potential / positive regulation of potassium ion transmembrane transport / cell volume homeostasis / CaM pathway / Cam-PDE 1 activation / Sodium/Calcium exchangers / phospholipid translocation / Calmodulin induced events / Reduction of cytosolic Ca++ levels / Activation of Ca-permeable Kainate Receptor / CREB1 phosphorylation through the activation of CaMKII/CaMKK/CaMKIV cascasde / Loss of phosphorylation of MECP2 at T308 / CREB1 phosphorylation through the activation of Adenylate Cyclase / PKA activation / negative regulation of high voltage-gated calcium channel activity / CaMK IV-mediated phosphorylation of CREB / Glycogen breakdown (glycogenolysis) / negative regulation of calcium ion export across plasma membrane / organelle localization by membrane tethering / Activation of RAC1 downstream of NMDARs / regulation of cardiac muscle cell action potential / mitochondrion-endoplasmic reticulum membrane tethering / CLEC7A (Dectin-1) induces NFAT activation / autophagosome membrane docking / immune system process / positive regulation of T cell receptor signaling pathway / positive regulation of ryanodine-sensitive calcium-release channel activity / Negative regulation of NMDA receptor-mediated neuronal transmission / regulation of cell communication by electrical coupling involved in cardiac conduction / Unblocking of NMDA receptors, glutamate binding and activation / negative regulation of peptidyl-threonine phosphorylation / Synthesis of IP3 and IP4 in the cytosol / Phase 0 - rapid depolarisation / protein phosphatase activator activity / RHO GTPases activate PAKs / positive regulation of cyclic-nucleotide phosphodiesterase activity / potassium channel activity / positive regulation of phosphoprotein phosphatase activity / Long-term potentiation / Ion transport by P-type ATPases / Uptake and function of anthrax toxins / Calcineurin activates NFAT / Regulation of MECP2 expression and activity / catalytic complex / DARPP-32 events / detection of calcium ion / Smooth Muscle Contraction / negative regulation of ryanodine-sensitive calcium-release channel activity / RHO GTPases activate IQGAPs / cellular response to interferon-beta / regulation of cardiac muscle contraction / calcium channel inhibitor activity / regulation of cardiac muscle contraction by regulation of the release of sequestered calcium ion / Protein methylation / voltage-gated potassium channel complex / Activation of AMPK downstream of NMDARs / eNOS activation / regulation of release of sequestered calcium ion into cytosol by sarcoplasmic reticulum / regulation of calcium-mediated signaling / positive regulation of protein dephosphorylation / titin binding / regulation of ryanodine-sensitive calcium-release channel activity / Tetrahydrobiopterin (BH4) synthesis, recycling, salvage and regulation / Ion homeostasis / positive regulation of protein autophosphorylation / potassium ion transmembrane transport / sperm midpiece / calcium channel complex / substantia nigra development / adenylate cyclase activator activity / Ras activation upon Ca2+ influx through NMDA receptor / regulation of heart rate / protein serine/threonine kinase activator activity / sarcomere / FCERI mediated Ca+2 mobilization / FCGR3A-mediated IL10 synthesis / VEGFR2 mediated vascular permeability / positive regulation of peptidyl-threonine phosphorylation / Antigen activates B Cell Receptor (BCR) leading to generation of second messengers / VEGFR2 mediated cell proliferation / regulation of cytokinesis / Translocation of SLC2A4 (GLUT4) to the plasma membrane / establishment of localization in cell / spindle microtubule / positive regulation of protein secretion / RAF activation / positive regulation of receptor signaling pathway via JAK-STAT / defense response / Transcriptional activation of mitochondrial biogenesis / positive regulation of protein serine/threonine kinase activity / potassium ion transport / Stimuli-sensing channels / spindle pole / cellular response to type II interferon / response to calcium ion
Similarity search - Function
Calmodulin-binding domain / Potassium channel, calcium-activated, SK / SK, calmodulin-binding domain superfamily / Calmodulin binding domain / Calcium-activated SK potassium channel / Calmodulin binding domain / Potassium channel domain / Ion channel / EF-hand domain pair / EF-hand, calcium binding motif ...Calmodulin-binding domain / Potassium channel, calcium-activated, SK / SK, calmodulin-binding domain superfamily / Calmodulin binding domain / Calcium-activated SK potassium channel / Calmodulin binding domain / Potassium channel domain / Ion channel / EF-hand domain pair / EF-hand, calcium binding motif / EF-Hand 1, calcium-binding site / EF-hand calcium-binding domain. / EF-hand calcium-binding domain profile. / EF-hand domain / EF-hand domain pair
Similarity search - Domain/homology
: / Chem-POV / Intermediate conductance calcium-activated potassium channel protein 4 / Calmodulin-1
Similarity search - Component
Biological speciesHomo sapiens (human)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.4 Å
AuthorsLee, C.H. / MacKinnon, R.
Funding support United States, 2items
OrganizationGrant numberCountry
National Institutes of Health/National Human Genome Research Institute (NIH/NHGRI)GM43949 United States
Howard Hughes Medical Institute (HHMI) United States
CitationJournal: Science / Year: 2018
Title: Activation mechanism of a human SK-calmodulin channel complex elucidated by cryo-EM structures.
Authors: Chia-Hsueh Lee / Roderick MacKinnon /
Abstract: Small-conductance Ca-activated K (SK) channels mediate neuron excitability and are associated with synaptic transmission and plasticity. They also regulate immune responses and the size of blood ...Small-conductance Ca-activated K (SK) channels mediate neuron excitability and are associated with synaptic transmission and plasticity. They also regulate immune responses and the size of blood cells. Activation of SK channels requires calmodulin (CaM), but how CaM binds and opens SK channels has been unclear. Here we report cryo-electron microscopy (cryo-EM) structures of a human SK4-CaM channel complex in closed and activated states at 3.4- and 3.5-angstrom resolution, respectively. Four CaM molecules bind to one channel tetramer. Each lobe of CaM serves a distinct function: The C-lobe binds to the channel constitutively, whereas the N-lobe interacts with the S4-S5 linker in a Ca-dependent manner. The S4-S5 linker, which contains two distinct helices, undergoes conformational changes upon CaM binding to open the channel pore. These structures reveal the gating mechanism of SK channels and provide a basis for understanding SK channel pharmacology.
History
DepositionMar 8, 2018Deposition site: RCSB / Processing site: RCSB
Revision 1.0May 2, 2018Provider: repository / Type: Initial release
Revision 1.1May 23, 2018Group: Data collection / Database references / Category: citation
Item: _citation.journal_volume / _citation.page_first ..._citation.journal_volume / _citation.page_first / _citation.page_last / _citation.pdbx_database_id_PubMed / _citation.title
Revision 1.2Nov 20, 2019Group: Author supporting evidence / Category: pdbx_audit_support / Item: _pdbx_audit_support.funding_organization
Revision 1.3Mar 13, 2024Group: Data collection / Database references / Derived calculations
Category: chem_comp_atom / chem_comp_bond ...chem_comp_atom / chem_comp_bond / database_2 / pdbx_struct_conn_angle / struct_conn
Item: _database_2.pdbx_DOI / _database_2.pdbx_database_accession ..._database_2.pdbx_DOI / _database_2.pdbx_database_accession / _pdbx_struct_conn_angle.ptnr1_auth_comp_id / _pdbx_struct_conn_angle.ptnr1_auth_seq_id / _pdbx_struct_conn_angle.ptnr1_label_atom_id / _pdbx_struct_conn_angle.ptnr1_label_comp_id / _pdbx_struct_conn_angle.ptnr1_label_seq_id / _pdbx_struct_conn_angle.ptnr2_auth_seq_id / _pdbx_struct_conn_angle.ptnr2_label_asym_id / _pdbx_struct_conn_angle.ptnr3_auth_comp_id / _pdbx_struct_conn_angle.ptnr3_auth_seq_id / _pdbx_struct_conn_angle.ptnr3_label_atom_id / _pdbx_struct_conn_angle.ptnr3_label_comp_id / _pdbx_struct_conn_angle.ptnr3_label_seq_id / _pdbx_struct_conn_angle.value / _struct_conn.pdbx_dist_value / _struct_conn.ptnr1_auth_asym_id / _struct_conn.ptnr1_auth_comp_id / _struct_conn.ptnr1_auth_seq_id / _struct_conn.ptnr1_label_asym_id / _struct_conn.ptnr1_label_atom_id / _struct_conn.ptnr1_label_comp_id / _struct_conn.ptnr1_label_seq_id / _struct_conn.ptnr2_auth_asym_id / _struct_conn.ptnr2_auth_comp_id / _struct_conn.ptnr2_auth_seq_id / _struct_conn.ptnr2_label_asym_id / _struct_conn.ptnr2_label_atom_id / _struct_conn.ptnr2_label_comp_id / _struct_conn.ptnr2_label_seq_id

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Structure visualization

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Assembly

Deposited unit
A: Intermediate conductance calcium-activated potassium channel protein 4
B: Intermediate conductance calcium-activated potassium channel protein 4
C: Intermediate conductance calcium-activated potassium channel protein 4
D: Intermediate conductance calcium-activated potassium channel protein 4
E: Calmodulin-1
F: Calmodulin-1
G: Calmodulin-1
H: Calmodulin-1
hetero molecules


Theoretical massNumber of molelcules
Total (without water)265,76525
Polymers258,4448
Non-polymers7,32117
Water0
1


  • Idetical with deposited unit
  • defined by author
  • Evidence: microscopy
TypeNameSymmetry operationNumber
identity operation1_5551
Buried area29170 Å2
ΔGint-193 kcal/mol
Surface area89370 Å2

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Components

#1: Protein
Intermediate conductance calcium-activated potassium channel protein 4 / SK4 channel / SKCa4 / IKCa1 / IK1 / KCa3.1 / KCa4 / Putative Gardos channel


Mass: 47758.496 Da / Num. of mol.: 4
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: KCNN4, IK1, IKCA1, KCA4, SK4 / Production host: Homo sapiens (human) / References: UniProt: O15554
#2: Protein
Calmodulin-1 /


Mass: 16852.545 Da / Num. of mol.: 4
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: CALM1, CALM, CAM, CAM1 / Production host: Homo sapiens (human) / References: UniProt: P0DP23
#3: Chemical
ChemComp-K / POTASSIUM ION


Mass: 39.098 Da / Num. of mol.: 5 / Source method: obtained synthetically / Formula: K
#4: Chemical
ChemComp-POV / (2S)-3-(hexadecanoyloxy)-2-[(9Z)-octadec-9-enoyloxy]propyl 2-(trimethylammonio)ethyl phosphate / POPC / POPC


Mass: 760.076 Da / Num. of mol.: 4 / Source method: obtained synthetically / Formula: C42H82NO8P / Comment: phospholipid*YM
#5: Sugar
ChemComp-LMT / DODECYL-BETA-D-MALTOSIDE


Type: D-saccharide / Mass: 510.615 Da / Num. of mol.: 8 / Source method: obtained synthetically / Formula: C24H46O11 / Comment: detergent*YM

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: human SK4/calmodulin channel complex / Type: COMPLEX / Entity ID: #1-#2 / Source: RECOMBINANT
Source (natural)Organism: Homo sapiens (human)
Source (recombinant)Organism: Homo sapiens (human)
Buffer solutionpH: 8
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationCryogen name: ETHANE

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: FEI TITAN KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELDBright-field microscopy
Image recordingElectron dose: 75 e/Å2 / Film or detector model: GATAN K2 SUMMIT (4k x 4k)

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Processing

SoftwareName: PHENIX / Version: 1.12_2829: / Classification: refinement
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
SymmetryPoint symmetry: C4 (4 fold cyclic)
3D reconstructionResolution: 3.4 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 42422 / Symmetry type: POINT
RefinementHighest resolution: 3.4 Å
Refine LS restraints
Refine-IDTypeDev idealNumber
ELECTRON MICROSCOPYf_bond_d0.02112807
ELECTRON MICROSCOPYf_angle_d0.89117328
ELECTRON MICROSCOPYf_dihedral_angle_d17.0717380
ELECTRON MICROSCOPYf_chiral_restr0.0542100
ELECTRON MICROSCOPYf_plane_restr0.0062108

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