scholarly journals Snapshots of actin and tubulin folding inside the TRiC chaperonin

2021 ◽  
Author(s):  
John J. Kelly ◽  
Dale Tranter ◽  
Els Pardon ◽  
Gamma Chi ◽  
Holger Kramer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Protein Folding ◽  
Structure Determination ◽  
Cytoskeletal Proteins ◽  
Chamber Wall ◽  
Atomistic Model ◽  
Structural Studies ◽  
Client Protein ◽  
Client Proteins ◽  
Unstructured Regions

AbstractThe integrity of a cell’s proteome depends on correct folding of polypeptides by chaperonins. The TCP-1 ring chaperonin (TRiC) acts as obligate folder for >10% of cytosolic proteins, including cytoskeletal proteins actin and tubulin. While its architecture and how it recognises folding substrates is emerging from structural studies, the subsequent fate of substrates inside the TRiC chamber is not defined. We trapped endogenous human TRiC with substrates (actin, tubulin) and co-chaperone (PhLP2A) at different folding stages, for structure determination by cryogenic electron microscopy. The already-folded regions of client proteins are anchored at the chamber wall, positioning unstructured regions towards the central space to achieve their folding. Substrates engage with different sections of the chamber during the folding cycle, coupled to TRiC open-and-close transitions. Furthermore, the cochaperone PhLP2A modulates folding, acting as a molecular strut between substrate and TRiC chamber. Our structural snapshots piece together an emerging atomistic model of client protein folding through TRiC.

Profile Imaging of Silicon Surface Reconstructions

1985 ◽  
Vol 43 ◽  
pp. 262-263
Author(s):  
O.L. Krivanek ◽  
G.J. Wood
Keyword(s):  
Electron Microscopy ◽  
Surface Structure ◽  
Structure Determination ◽  
Silicon Surface ◽  
Good Resolution ◽  
Surface Reconstructions ◽  
Bulk Structure ◽  
Point To Point ◽  
The Relationship

Electron microscopy at 0.2nm point-to-point resolution, 10-10 torr specimei region vacuum and facilities for in-situ specimen cleaning presents intere; ing possibilities for surface structure determination. Three methods for examining the surfaces are available: reflection (REM), transmission (TEM) and profile imaging. Profile imaging is particularly useful because it giv good resolution perpendicular as well as parallel to the surface, and can therefore be used to determine the relationship between the surface and the bulk structure.

Structural studies on crystals found in the intestine of Nematodirus battus

1980 ◽  
Vol 208 (1173) ◽  
pp. 409-414
Keyword(s):  
Electron Microscopy ◽  
Unit Cell ◽  
Structural Studies ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Crystals found in the lumen of the intestine of Nematodirus battus have been studied by electron microscopy. Two of the unit cell dimensions are 16 nm x 23 nm. The possibility of an immunological significance for these crystals is considered.

scholarly journals In situ structure determination using single particle cryo-electron microscopy images

2020 ◽  
Author(s):  
Jing Cheng ◽  
Bufan Li ◽  
Long Si ◽  
Xinzheng Zhang
Keyword(s):  
Electron Microscopy ◽  
Structure Determination ◽  
Single Particle ◽  
Structure Refinement ◽  
Target Function ◽  
Target Protein ◽  
Particle Analysis ◽  
Cryo Electron Microscopy ◽  
Tilt Series

AbstractCryo-electron microscopy (cryo-EM) tomography is a powerful tool for in situ structure determination. However, this method requires the acquisition of tilt series, and its time consuming throughput of acquiring tilt series severely slows determination of in situ structures. By treating the electron densities of non-target protein as non-Gaussian distributed noise, we developed a new target function that greatly improves the efficiency of the recognition of the target protein in a single cryo-EM image without acquiring tilt series. Moreover, we developed a sorting function that effectively eliminates the false positive detection, which not only improves the resolution during the subsequent structure refinement procedure but also allows using homolog proteins as models to recognize the target protein. Together, we developed an in situ single particle analysis (isSPA) method. Our isSPA method was successfully applied to solve structures of glycoproteins on the surface of a non-icosahedral virus and Rubisco inside the carboxysome. The cryo-EM data from both samples were collected within 24 hours, thus allowing fast and simple structural determination in situ.

scholarly journals A resolution record for cryoEM

2021 ◽  
Vol 10 ◽  
Author(s):  
Jonathan Ashmore ◽  
Bridget Carragher ◽  
Peter B Rosenthal ◽  
William Weis
Keyword(s):  
Electron Microscopy ◽  
Image Analysis ◽  
Structure Determination ◽  
Test Specimen ◽  
Structural Information ◽  
Atomic Resolution ◽  
Fast Growing ◽  
Cryo Electron Microscopy ◽  
New Instrument ◽  
Resolution Structure

Cryo electron microscopy (cryoEM) is a fast-growing technique for structure determination. Two recent papers report the first atomic resolution structure of a protein obtained by averaging images of frozen-hydrated biomolecules. They both describe maps of symmetric apoferritin assemblies, a common test specimen, in unprecedented detail. New instrument improvements, different in the two studies, have contributed better images, and image analysis can extract structural information sufficient to resolve individual atomic positions. While true atomic resolution maps will not be routine for most proteins, the studies suggest structures determined by cryoEM will continue to improve, increasing their impact on biology and medicine.

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