Journal: Cell Rep / Year: 2018 Title: Classification of Single Particles from Human Cell Extract Reveals Distinct Structures. Authors: Eric J Verbeke / Anna L Mallam / Kevin Drew / Edward M Marcotte / David W Taylor / Abstract: Multi-protein complexes are necessary for nearly all cellular processes, and understanding their structure is required for elucidating their function. Current high-resolution strategies in structural ...Multi-protein complexes are necessary for nearly all cellular processes, and understanding their structure is required for elucidating their function. Current high-resolution strategies in structural biology are effective but lag behind other fields (e.g., genomics and proteomics) due to their reliance on purified samples rather than heterogeneous mixtures. Here, we present a method combining single-particle analysis by electron microscopy with protein identification by mass spectrometry to structurally characterize macromolecular complexes from human cell extract. We identify HSP60 through two-dimensional classification and obtain three-dimensional structures of native proteasomes directly from ab initio classification of a heterogeneous mixture of protein complexes. In addition, we reveal an ∼1-MDa-size structure of unknown composition and reference our proteomics data to suggest possible identities. Our study shows the power of using a shotgun approach to electron microscopy (shotgun EM) when coupled with mass spectrometry as a tool to uncover the structures of macromolecular machines.
History
Deposition
May 29, 2018
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Header (metadata) release
Jun 20, 2018
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Map release
Jul 18, 2018
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Update
Jul 18, 2018
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Current status
Jul 18, 2018
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Material: COPPER / Mesh: 400 / Support film - Material: CARBON / Support film - topology: CONTINUOUS / Support film - Film thickness: 1000.0 nm
Details
The sample was monodisperse.
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Electron microscopy
Microscope
JEOL 2100
Image recording
Film or detector model: GATAN MULTISCAN / Number grids imaged: 1 / Number real images: 1500 / Average exposure time: 1.0 sec. / Average electron dose: 30.0 e/Å2
Electron beam
Acceleration voltage: 200 kV / Electron source: FIELD EMISSION GUN
Electron optics
Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD
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Image processing
Particle selection
Number selected: 35000
CTF correction
Software - Name: CTFFIND (ver. 4)
Final reconstruction
Resolution.type: BY AUTHOR / Resolution: 31.0 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: RELION (ver. 2) / Number images used: 1121
Initial angle assignment
Type: NOT APPLICABLE
Final angle assignment
Type: NOT APPLICABLE
Final 3D classification
Number classes: 30 / Software - Name: RELION (ver. 2)
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