Table 1.
Cryo-EM Statistics for Data Collection and Model Refinement
| Cas1-Cas2-Csn2 Monomer (EMD-4668; PDB: 6QXF) | Cas1-Cas2-Csn2 Dimer (EMD-4670; PDB: 6QXT) | Cas1-Cas2-Csn2 Filament (EMD-4671; PDB: 6QY3) | |
|---|---|---|---|
| Data Collection | |||
| Microscope | Titan Krios | |Titan Krios | Titan Krios |
| Camera | FEI Falcon III (integrating) | FEI Falcon III (integrating) | FEI Falcon III (integrating) |
| Voltage (kV) | 300 | 300 | 300 |
| Magnification | 75,000 | 75,000 | 75,000 |
| Pixel size (Å) | 1.085 | 1.085 | 1.085 |
| Electron dose (e−/Å2) | 92.8 | 92.8 | 92.8 |
| Dose rate (e−/pixel/s) | 109.2 | 109.2 | 109.2 |
| Defocus range (μm) | −1.3 to −2.8 | −1.3 to −2.8 | −1.3 to −2.8 |
| Final particles (no.) | 306,389 | 3,109 | 66,576 |
| Symmetry imposed | C1 | C1 | C1 |
| Map resolution (Å) | 3.6 | 8.9 | 9.1 |
| Map sharpening B-factor (Å2) | −80 | −250 | −300 |
| Model Composition | |||
| Nonhydrogen atoms | 34,693 | 59,686 | 54,986 |
| Protein residues | 4,138 | 11,688a | 10,664a |
| DNA bases | 50 | 108 | 132 |
| Ca2+ ligands | 8 | 16 | 16 |
| Refinement | |||
| Initial PDB templates | PDB: 3V7F; PDB: 5XVN | PDB: 5ZYF; PDB: 6QXF | PDB: 6QXF |
| FSC (entire box) | 0.90 | 0.85 | 0.80 |
| FSC (around atoms) | 0.87 | 0.71 | 0.66 |
| RMS Deviations | |||
| Bond lengths (Å) | 0.002 | 0.001 | 0.001 |
| Bond angles (°) | 0.41 | 0.42 | 0.37 |
| Validation | |||
| Clashscore | 6.9 | 0.9a | 1.1a |
| Poor rotamers (%) | 0.7 | NAa | NAa |
| Ramachandran Plot | |||
| Favored (%) | 97.7 | 97.6 | 97.6 |
| Allowed (%) | 2.2 | 2.3 | 2.3 |
| Disallowed (%) | 0.1 | 0.1 | 0.1 |
FSC, Fourier shell correlation; RMS, root mean square
a
Residues clipped at the C α positions