ELECTRON MICROSCOPY

Sample

cryoEM structure of mTORC1 bound to RagA/C complex

Specimen Preperation
Sample Aggregation State PARTICLE
Vitrification Instrument FEI VITROBOT MARK III
Cryogen Name ETHANE
Sample Vitrification Details ?
3D Reconstruction
Reconstruction Method SINGLE PARTICLE
Number of Particles 90809
Reported Resolution (Å) 5.5
Resolution Method FSC 0.143 CUT-OFF
Other Details For the final reconstruction of mTORC1-RagA/C structure we used a strategy taking advantage of the relion particle symmetry expand program, and duplicated the C2-refined particles and applied the appropriate rotation and translation to generate a set of monomers. We performed mTORC1-RagA/C 'pseudo-monomer' focussed classification with signal subtraction and obtained a reconstruction of 5.5 A resolution map. This cryo-EM density corresponded to the mTORC1-RagA/C pseudomonomer, where the previously published structure for apo-mTORC1 (PDB ID 6BCX) and our high-resolution crystal structure of RagA/C (6S6A) were fitted with great confidence from our experimental analysis including Pulldown assays, mutational at per-residue level in the binding interface and HDX-Mass Spectrometry.
Refinement Type
Symmetry Type POINT
Map-Model Fitting and Refinement
ID 1
Refinement Space REAL
Refinement Protocol RIGID BODY FIT
Refinement Target ?
Overall B Value 283
Fitting Procedure ?
Details Cryo-EM model of mTORC1-RagA/C was refined using REFMAC5 program in CCPEM package, with a composite map of the 3D reconstruction of mTORC1-RagA/C pseudo-monomer (as mentioned in Reconstruction section) of one protomer together with the generated map for the other second protomer of mTORC1-RagA/C. This second protomer of mTORC1-RagA/C map was generated by simply aligning the first 3D reconstructed pseudomonomer map onto the mTORC1 dimer consensus C2 map and then obtained the rotation-translation matrix with CHIMERA and then used Maputils program in CCP4i. From the resulting mTORC1-RagA/C dimer map, the model of mTORC1-RagA/C was built by using previously published structure of apo-mTORC1 (PDB ID 6BCX) and our crystal structure of RagA/C was fitted (PDB ID 6S6A, unreleased). The entire mTORC1-RagA/C final model was refined using REFMAC5 program using the restraints from the crystal structure of RagA/C and previously published mTORC1 structure. Side chains were removed before refinement, since these were not evident in the cryo-EM densities. Separate model refinements were performed against single half-maps, and the resulting models were compared with the other half-maps to confirm the absence of overfitting.
Data Acquisition
Detector Type GATAN K2 SUMMIT (4k x 4k)
Electron Dose (electrons/Å2) 40
Imaging Experiment
Date of Experiment ?
Temprature (Kelvin)
Microscope Model FEI TITAN KRIOS
Minimum Defocus (nm) ?
Maximum Defocus (nm) ?
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 ?
Imaging Experiment
Task Software Package Version
PARTICLE SELECTION RELION 3.0.3
IMAGE ACQUISITION EPU 1.10.0.77REL
CTF CORRECTION Gctf 1.18
MODEL FITTING REFMAC 5.8.0238
MODEL REFINEMENT REFMAC 5.8.0238
INITIAL EULER ASSIGNMENT RELION 3.0.6
FINAL EULER ASSIGNMENT RELION 3.0.6
CLASSIFICATION RELION 3.0.6
RECONSTRUCTION RELION 3.0.6
Image Processing
CTF Correction Type CTF Correction Details Number of Particles Selected Particle Selection Details
PHASE FLIPPING AND AMPLITUDE CORRECTION ?