6ND0

human BK channel reconstituted into liposomes

ELECTRON MICROSCOPY

Sample
human BK channel reconstituted into liposomes

Specimen Preparation
Sample Aggregation State	PARTICLE
Vitrification Instrument	FEI VITROBOT MARK IV
Cryogen Name	ETHANE
Sample Vitrification Details	BK proteoliposomes were applied onto a glow-discharged perforated carbon grid (CFlat R2/2, EMS), and incubated for 5-10 min In an FEI Vitrobot Mark IV ...	BK proteoliposomes were applied onto a glow-discharged perforated carbon grid (CFlat R2/2, EMS), and incubated for 5-10 min In an FEI Vitrobot Mark IV (FEI). After incubation, the sample was blotted from the side and buffer containing 10 mM HEPES, pH 7.3, 75 mM KCl, and 1 mM EDTA was applied onto the TEM grid to further swell proteoliposomes. Then grids were blotted for 7 s with force 0 and fast frozen in liquid ethane cooled by liquid nitrogen.

3D Reconstruction
Reconstruction Method	SINGLE PARTICLE
Number of Particles	122456
Reported Resolution (Å)	3.5
Resolution Method	FSC 0.143 CUT-OFF
Other Details
Refinement Type
Symmetry Type	POINT
Point Symmetry	C2

Map-Model Fitting and Refinement
Id	1
Refinement Space	REAL
Refinement Protocol	FLEXIBLE FIT
Refinement Target
Overall B Value
Fitting Procedure
Details

Data Acquisition
Detector Type	GATAN K2 SUMMIT (4k x 4k)
Electron Dose (electrons/Å**2)	60

Imaging Experiment	1
Date of Experiment
Temperature (Kelvin)
Microscope Model	FEI TITAN KRIOS
Minimum Defocus (nm)	852
Maximum Defocus (nm)	4000
Minimum Tilt Angle (degrees)
Maximum Tilt Angle (degrees)
Nominal CS	2.7
Imaging Mode	BRIGHT FIELD
Specimen Holder Model	FEI TITAN KRIOS AUTOGRID HOLDER
Nominal Magnification	130000
Calibrated Magnification
Source	FIELD EMISSION GUN
Acceleration Voltage (kV)	300
Imaging Details	The Coma free alignment was performed using Auto-CTF software from FEI.

EM Software
Task	Software Package	Version
PARTICLE SELECTION	RELION	2.1
PARTICLE SELECTION	MATLAB	R2018a
IMAGE ACQUISITION	Leginon	3.3
CTF CORRECTION	CTFFIND	4
CTF CORRECTION	Gctf
INITIAL EULER ASSIGNMENT	RELION	2.1
FINAL EULER ASSIGNMENT	RELION	2.1
CLASSIFICATION	RELION	2.1
RECONSTRUCTION	RELION	2.1

Image Processing
CTF Correction Type	CTF Correction Details	Number of Particles Selected	Particle Selection Details
PHASE FLIPPING AND AMPLITUDE CORRECTION	CTF full correction was performed following RELION 3D reconstruction	275295	Approximately 4,800 particles from 350 micrographs were interactively selected and classified using RELION. Ten representative classes were selected as the templates for automated particle picking using RELION. The automated picked particles were screened using homemade MATLAB (MathWorks) programs to exclude particles more than 80 A away from any liposome, which resulted in 275,295 particles from 2,786 micrographs.

RCSB PDB Core Operations are funded by the U.S. National Science Foundation (DBI-2321666), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM133198.