K2 Summit camera enables scientists to generate the first atomic model of an intact, functional spliceosome using cryo-electron microscopy

November 06, 2015

In structural biology, many biologically interesting structures have remained a mystery; often because they are too dynamic to be crystalized effectively. With the shift to single-particle cryo-electron microscopy (cryo-EM), some of these challenging structures are starting to reveal their secrets.

Recently the Gatan K2 Summit® direct detection camera was the key detector used to solve structures to better than 3 Å (angstrom) resolution. However recent work has also proven that resolution is not the only benefit of using this camera in cryo-EM.  

The recent work, spearheaded by Professor Yigoing Shi, Vice President of Tsinghua University in China, described the 3.6 Å structure of a yeast (Schizosaccharomyces pombe) spliceosome. Structure of a yeast spliceosome at 3.6-angstom resolution, 10.1126/science.aac7629.

Previously, elucidation of the spliceosome’s molecular mechanisms and the splicing reaction required detailed structural information on the intact spliceosome at different stages of its action. The large spliceosome size and dynamic nature of each splicing reaction cycle has prevented crystallization of the entire spliceosome.

“Splicing of pre-messenger RNA (pre-mRNA) is executed by the spliceosomes, which are large and relative flexible complexes. Using single-particle cryo-EM with the K2 Summit direct detection camera, we finally got this complicated structure solved, reaching an overall 3.6 Å resolution and a large portion around 2.9~3.3 Å,” states Professor Shi.

He continues, “This is an extremely variable and diverse macromolecule. The high resolution regions helped us to identify proteins and sequences directly from the density, and enabled de-novo model building. The K2 Summit camera, which uses electron counting to record the highest resolution images and lower the noise, really played a key role in allowing us get this high resolution structure.”

“This structure is truly a major step forward for the field of cryo-EM. The high contrast and high resolution images from the K2 Summit camera have made it possible to analyze such a dynamic structure at very high resolution,” explains Christopher Booth, Life Science Product Manager at Gatan. “We are gratified that the K2 Summit camera is being used to solve important structures of biological and medical significance.”

About Cryo-EM

Cryo-EM is emerging as a major tool in a structural biologist’s arsenal, alongside conventional x-ray crystallography and NMR techniques, to study molecular interactions in supramolecular assemblies or biological machines.

Cryo-EM enables structure-based examination of native and hydrated biological complexes such as viruses, small organelles, and macromolecular biological complexes of 150 kDa or larger. Compared to conventional techniques, single-particle cryo-EM can provide resolutions approaching 2 Å for stable samples and allows you to obtain meaningful results with samples that are heterogeneous, metastable and extremely difficult to crystalize.

For more information regarding the K2 direct detection camera, please visit: http://www.gatan.com/K2


About Gatan Inc.

Gatan, Inc. is the world's leading manufacturer of instrumentation and software used to enhance and extend the operation and performance of electron microscopes. Gatan products, which are fully compatible with nearly all electron microscope models, cover the entire range of the research process—from specimen preparation and manipulation to imaging and analysis. For more information, visit www.gatan.com.

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