7ZBU

CryoEM structure of SARS-CoV-2 spike monomer in complex with neutralising antibody P008_60

ELECTRON MICROSCOPY

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Refinement

RMS Deviations
Key	Refinement Restraint Deviation
f_dihedral_angle_d	5.394
f_angle_d	0.66
f_chiral_restr	0.052
f_plane_restr	0.005
f_bond_d	0.003

Sample
Monomeric Spike glycoprotein ectodomain from SARS-CoV-2 in complex with a neutralising antibody P008_60

Specimen Preparation
Sample Aggregation State	PARTICLE
Vitrification Instrument	FEI VITROBOT MARK IV
Cryogen Name	ETHANE
Sample Vitrification Details	blotted for 3 to 4 sec before plunging

3D Reconstruction
Reconstruction Method	SINGLE PARTICLE
Number of Particles	166619
Reported Resolution (Å)	4.31
Resolution Method	FSC 0.143 CUT-OFF
Other Details	Non Uniform refinement in cryoSPARC
Refinement Type
Symmetry Type	POINT
Point Symmetry	C1

Map-Model Fitting and Refinement
Id	1 (7A92, 5WI9, 5WI9)
Refinement Space	REAL
Refinement Protocol	OTHER
Refinement Target	Correlation coefficient
Overall B Value	81
Fitting Procedure
Details	The atomistic models of monomeric SARS-CoV-2 S1 protein and a Fab molecule, extracted from PDB entries 7A92 and 5WI9, were docked in the cryo-EM map using Chimera. The NTD and the RBD of the spike subunit were replaced with the crystal structures from PDB entries 7B62 and 7OAO, respectively. Guided by the cryo-EM map, the model was adjusted and extended interactively in Coot and refined using phenix.real_space_refine.

Data Acquisition
Detector Type	GATAN K3 (6k x 4k)
Electron Dose (electrons/Å**2)	50

Imaging Experiment	1
Date of Experiment
Temperature (Kelvin)
Microscope Model	FEI TITAN KRIOS
Minimum Defocus (nm)	700
Maximum Defocus (nm)	3600
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
Calibrated Magnification
Source	FIELD EMISSION GUN
Acceleration Voltage (kV)	300
Imaging Details

EM Software
Task	Software Package	Version
PARTICLE SELECTION	Gautomatch	0.53
IMAGE ACQUISITION	EPU
CTF CORRECTION	Gctf	1.06
MODEL FITTING	UCSF Chimera
CLASSIFICATION	RELION	3.1
RECONSTRUCTION	cryoSPARC	2
MODEL REFINEMENT	PHENIX	4213

Image Processing
CTF Correction Type	CTF Correction Details	Number of Particles Selected	Particle Selection Details
PHASE FLIPPING AND AMPLITUDE CORRECTION		1740430	Initially, particles were picked with Gautomatch-v0.53 using 2D class averages of the trimeric spike, low-pass filtered to 20 A resolution, as templates. The resulting 1,740,430 particles, extracted in Relion-3.1 and binned to a pixel size of 4.4 A, were subjected to two rounds of reference-free 2D classification in cryoSPARC-2. 283,956 particles belonging to well-defined 2D classes were subjected to classification into twelve 3D classes in Relion-3.1. Neither the 2D nor 3D class averages of the trimeric spike revealed features attributable to a bound Fab molecule. Next, 3,772,722 particles were picked using 2D class averages of the dissociated spikes. Following two rounds of 2D classification in cryoSPARC-2, 753,837 particles, re-extracted with pixel size of 2.2 A, were subjected to 3D classification in Relion-3.1 into 9 classes using an initial model obtained by Ab-initio reconstruction in cryoSPARC-2. The procedure revealed a single well-defined 3D class containing 208,343 particles (27.4%) of S1 protein with a bound Fab molecule. The particles, re-extracted without binning (with a pixel size 1.1 A), were subjected to two rounds of 3D classification using Ab-initio reconstruction in cryoSPARC-2 with 2 classes and class similarity set to 0. At the end of each round, the most populated class was selected, resulting in the final set of 166,619 particles.