2018-01-03 REL PDBe PDBe PDBe 2017-10-17 2017-10-25 2017-10-25 2018-01-03 Albert S Schaffer M Beck F Mosalaganti S Asano S Thomas HF Plitzko J Beck M Baumeister W Engel BD Albert S Schaffer M Beck F Mosalaganti S Asano S Thomas HF Plitzko JM Beck M Baumeister W Engel BD Proc. Natl. Acad. Sci. U.S.A. US 114 13726 13731 2017 29229809 doi:10.1073/pnas.1716305114 1091-6490 0040 PNASA6 EMD-3938 associated EM volume In situ free 26S proteasome In situ free 26S proteasome 0

In situ subtomogram average generated from free 26S proteasomes imaged within the native Chlamydomonas cell. Cells were thinned by focused ion beam milling.

Chlamydomonas reinhardtii mat3-4 2 subtomogramAveraging cell 7. Quantifoil R2/1 COPPER 200 GLOW DISCHARGE AIR ETHANE-PROPANE 90 293 FEI VITROBOT MARK IV

Blotted for 10 seconds with 10 blot force before plunging..

Free 26S proteasome within the nucleus and cytoplasm of the native Chlamydomonas cell. Whole cells were plunge-frozen onto EM grids and then thinned with a cryo-focused ion beam instrument.

FEI TITAN KRIOS FLOOD BEAM BRIGHT FIELD FIELD EMISSION GUN 300 2.7 4.0 6.0 42000. FEI TITAN KRIOS AUTOGRID HOLDER NITROGEN GIF Quantum LS 0 20 GATAN K2 SUMMIT (4k x 4k) COUNTING 3838 3710 1.5 1.5

Images were collected in movie mode at 12 frames per second

1 C1 BACK PROJECTION 23.81 FSC 0.143 CUT-OFF RELION

For the final reconstruction, the tilt series was restricted between -30 and +30 degrees.

2116 76 3385 EMDB: 2165, lowpass filtered, one masked cap automated template matching PyTom template matching

Extracted proteasomes were cut in half along the medial axis of the 20S core particle, treating each half as an individual particle.

CTFFIND 4 CTFFIND was used with the Relion package PyTom We used several rounds of autofocused 3D classification (AC3D) NOT APPLICABLE RELION