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- PDB-7unm: Human TMEM175 in an closed state -

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Basic information

Entry
Database: PDB / ID: 7unm
TitleHuman TMEM175 in an closed state
ComponentsEndosomal/lysosomal potassium channel TMEM175
KeywordsMEMBRANE PROTEIN / potassium channel
Function / homology
Function and homology information


lysosomal lumen pH elevation / phagosome-lysosome fusion / regulation of lysosomal lumen pH / potassium ion leak channel activity / proton channel activity / arachidonic acid binding / potassium channel activity / potassium ion transmembrane transport / proton transmembrane transport / neuron cellular homeostasis ...lysosomal lumen pH elevation / phagosome-lysosome fusion / regulation of lysosomal lumen pH / potassium ion leak channel activity / proton channel activity / arachidonic acid binding / potassium channel activity / potassium ion transmembrane transport / proton transmembrane transport / neuron cellular homeostasis / lysosome / endosome membrane / endosome / lysosomal membrane
Similarity search - Function
Endosomal/lysomomal potassium channel TMEM175 / Endosomal/lysosomal potassium channel TMEM175
Similarity search - Domain/homology
: / Endosomal/lysosomal proton channel TMEM175
Similarity search - Component
Biological speciesHomo sapiens (human)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 2.61 Å
AuthorsOh, S. / Hite, R.K.
Funding support United States, 3items
OrganizationGrant numberCountry
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)GM141553 United States
National Institutes of Health/National Cancer Institute (NIH/NCI)CA008748 United States
National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI) United States
CitationJournal: Elife / Year: 2022
Title: Differential ion dehydration energetics explains selectivity in the non-canonical lysosomal K channel TMEM175.
Authors: SeCheol Oh / Fabrizio Marinelli / Wenchang Zhou / Jooyeon Lee / Ho Jeong Choi / Min Kim / José D Faraldo-Gómez / Richard K Hite /
Abstract: Structures of the human lysosomal K channel transmembrane protein 175 (TMEM175) in open and closed states revealed a novel architecture lacking the canonical K selectivity filter motif present in ...Structures of the human lysosomal K channel transmembrane protein 175 (TMEM175) in open and closed states revealed a novel architecture lacking the canonical K selectivity filter motif present in previously known K channel structures. A hydrophobic constriction composed of four isoleucine residues was resolved in the pore and proposed to serve as the gate in the closed state, and to confer ion selectivity in the open state. Here, we achieve higher-resolution structures of the open and closed states and employ molecular dynamics simulations to analyze the conducting properties of the putative open state, demonstrating that it is permeable to K and, to a lesser degree, also Na. Both cations must dehydrate significantly to penetrate the narrow hydrophobic constriction, but ion flow is assisted by a favorable electrostatic field generated by the protein that spans the length of the pore. The balance of these opposing energetic factors explains why permeation is feasible, and why TMEM175 is selective for K over Na, despite the absence of the canonical selectivity filter. Accordingly, mutagenesis experiments reveal an exquisite sensitivity of the channel to perturbations that mitigate the constriction. Together, these data reveal a novel mechanism for selective permeation of ions by TMEM175 that is unlike that of other K channels.
History
DepositionApr 11, 2022Deposition site: RCSB / Processing site: RCSB
Revision 1.0Jun 29, 2022Provider: repository / Type: Initial release
Revision 1.1Feb 14, 2024Group: Data collection / Category: chem_comp_atom / chem_comp_bond

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

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Assembly

Deposited unit
B: Endosomal/lysosomal potassium channel TMEM175
A: Endosomal/lysosomal potassium channel TMEM175
hetero molecules


Theoretical massNumber of molelcules
Total (without water)111,5307
Polymers111,3342
Non-polymers1955
Water99155
1


  • Idetical with deposited unit
  • defined by author
TypeNameSymmetry operationNumber
identity operation1_5551

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Components

#1: Protein Endosomal/lysosomal potassium channel TMEM175 / Transmembrane protein 175 / hTMEM175


Mass: 55667.219 Da / Num. of mol.: 2
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: TMEM175 / Production host: Homo sapiens (human) / References: UniProt: Q9BSA9
#2: Chemical
ChemComp-K / POTASSIUM ION


Mass: 39.098 Da / Num. of mol.: 5 / Source method: obtained synthetically / Formula: K / Feature type: SUBJECT OF INVESTIGATION
#3: Water ChemComp-HOH / water / Water


Mass: 18.015 Da / Num. of mol.: 55 / Source method: isolated from a natural source / Formula: H2O
Has ligand of interestY

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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: TMEM175 / Type: COMPLEX / Entity ID: #1 / Source: RECOMBINANT
Molecular weightExperimental value: NO
Source (natural)Organism: Homo sapiens (human)
Source (recombinant)Organism: Homo sapiens (human)
Buffer solutionpH: 8
Buffer component
IDConc.NameFormulaBuffer-ID
10.1 %Lauryl maltose neopentyl glycol1
250 mMTris pH 8.01
3150 mMPotassium ChlorideKCl1
42 mMDithiothreitol1
SpecimenConc.: 4 mg/ml / Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
Specimen supportGrid material: GOLD / Grid mesh size: 400 divisions/in. / Grid type: Quantifoil R1.2/1.3
VitrificationInstrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Humidity: 100 % / Chamber temperature: 298 K

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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 / Nominal defocus max: 2500 nm / Nominal defocus min: 800 nm
Image recordingElectron dose: 61 e/Å2 / Film or detector model: GATAN K2 SUMMIT (4k x 4k)
Image scansMovie frames/image: 40

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Processing

SoftwareName: PHENIX / Version: 1.19.1_4122: / Classification: refinement
EM software
IDNameCategory
1RELIONparticle selection
4CTFFINDCTF correction
9PHENIXmodel refinement
10cryoSPARCinitial Euler assignment
11cryoSPARCfinal Euler assignment
13cryoSPARC3D reconstruction
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
Particle selectionNum. of particles selected: 4153614
3D reconstructionResolution: 2.61 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 163651 / Algorithm: FOURIER SPACE / Num. of class averages: 1 / Symmetry type: POINT
Refine LS restraints
Refine-IDTypeDev idealNumber
ELECTRON MICROSCOPYf_bond_d0.0025848
ELECTRON MICROSCOPYf_angle_d0.427970
ELECTRON MICROSCOPYf_dihedral_angle_d3.623782
ELECTRON MICROSCOPYf_chiral_restr0.035980
ELECTRON MICROSCOPYf_plane_restr0.004978

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