8C8N

In situ structure of the Nitrosopumilus maritimus S-layer - Two-fold symmetry (C2)

ELECTRON MICROSCOPY

Refinement

RMS Deviations
Key	Refinement Restraint Deviation
f_dihedral_angle_d	4.263
f_angle_d	0.458
f_chiral_restr	0.043
f_plane_restr	0.003
f_bond_d	0.002

Sample
Nitrosopumilus maritimus S-layer

Specimen Preparation
Sample Aggregation State	CELL
Vitrification Instrument	FEI VITROBOT MARK IV
Cryogen Name	NITROGEN
Sample Vitrification Details	absorption for 60 sec and blotted for 5 sec with blot force -10

3D Reconstruction
Reconstruction Method	SUBTOMOGRAM AVERAGING
Number of Particles	108621
Reported Resolution (Å)	3.4
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	RECIPROCAL
Refinement Protocol	AB INITIO MODEL
Refinement Target	Best Fit
Overall B Value	66.19
Fitting Procedure
Details

Data Acquisition
Detector Type	GATAN K2 SUMMIT (4k x 4k)
Electron Dose (electrons/Å**2)	2.96

Imaging Experiment	1
Date of Experiment
Temperature (Kelvin)
Microscope Model	FEI TITAN KRIOS
Minimum Defocus (nm)	2000
Maximum Defocus (nm)	5000
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	105000
Calibrated Magnification	105000
Source	FIELD EMISSION GUN
Acceleration Voltage (kV)	300
Imaging Details

EM Software
Task	Software Package	Version
VOLUME SELECTION	RELION	4.0.0
IMAGE ACQUISITION	SerialEM
CTF CORRECTION	CTFFIND	4.1.13
CTF CORRECTION	RELION	4.0.0
MODEL FITTING	Coot	0.9.2-pre
MODEL REFINEMENT	PHENIX	1.19-4092
MODEL REFINEMENT	REFMAC
INITIAL EULER ASSIGNMENT	RELION	3.1
FINAL EULER ASSIGNMENT	RELION	4.0.0
CLASSIFICATION	RELION	4.0.0
RECONSTRUCTION	RELION	4.0.0

Image Processing
CTF Correction Type	CTF Correction Details	Number of Particles Selected	Particle Selection Details
PHASE FLIPPING AND AMPLITUDE CORRECTION	PseudoSubtomograms as described in Zivanov 2022 (https://elifesciences.org/articles/83724)	1971908	Initially, side views of S-layer sheets were first manually picked along the edge of the lattice using the helical picking tab in RELION while setting the helical rise to 60 angstrom. Top and tilted views were manually picked at the central hexameric axis. Manually picked particles were extracted in 4x downsampled 128x128 pixel2 boxes and classified using reference-free 2D classification inside RELION-3.1. Class averages centered at a hexameric axis were used to automatically pick particles inside RELION-3.1. Automatically picked particles were extracted in 4x downsampled 128x128 pixel2 boxes and classified using reference-free 2D classification. Particle coordinates belonging to class averages centered at the hexameric axis were used to train TOPAZ in 5x downsampled micrographs with the neural network architecture conv127. For the final reconstruction, particles were picked using TOPAZ and the previously trained neural network above. Additionally, top, bottom, and side views were picked using the reference-based autopicker inside RELION-3.1, which TOPAZ did not readily identify. Particles were extracted in 4x downsampled 128x128 pixel2 boxes and classified using reference-free 2D classification inside RELION-3.1. Particles belonging to class averages centered at the hexameric axis were combined, and particles within 30 angstrom were removed to prevent duplication after alignment. All resulting particles were then re-extracted in 4x downsampled 128x128 pixel2 boxes.

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 R01GM157729.