ELECTRON CRYO-MICROSCOPY OF BIOMOLECULES AT ATOMIC RESOLUTION
Wah Chiu
SLAC National Accelerator Laboratory, Menlo Park, CA, USA, Department of Bioengineering, Stanford University, Stanford, CA, USA
Single particle electron cryo-microscopy (cryo-EM) is a mature methodology for routine structure determination with detailed features equivalent to those obtained by X-ray crystallography at comparable resolutions. There are more than 4,000 cryo-EM structures better than 4 Å resolution deposited to the protein databank as in early 2021. Cryo-EM has the resolving power to visualize atomic details of biomolecules [1]. Quantitative metrics have been developed to assess the accuracy of the atomic model and its agreement with the reconstructed 3D density [2]. A distinct advantage of cryo-EM is the specimen requirement that the purified macromolecules for cryo-EM do not need to be crystallized nor to have uniform conformation and/or composition. The image processing method has been developed that one can sort out the images with structural heterogeneities [3]. Excitingly, one would be able to derive multiple structures from a single biochemically purified biomolecules [4]. Furthermore, cryo-EM can resolve structural variants among individual particles [5]. We are entering a new era on the investigation of single particle structural biophysics and begin asking biochemical questions of biomolecules different from the traditional methods.
References
[1] Zhang, K, Pintilie, GD, Li, S, Schmid, MF, & Chiu, W (2020) Resolving individual atoms of protein complex by cryo-electron microscopy. Cell Res 30(12):1136-1139.
[2] Lawson, CL, Kryshtafovych, A, et al. (2021) Cryo-EM model validation recommendations based on outcomes of the 2019 EMDataResource challenge. Nat Methods 18(2):156-164.
[3] Scheres, SH (2016) Processing of Structurally Heterogeneous Cryo-EM Data in RELION. Methods Enzymol 579:125-157.
[4] Roh, SH, Shekhar, M, Pintilie, G, Chipot, C, Wilkens, S, Singharoy, A, & Chiu, W (2020) Cryo-EM and MD infer water-mediated proton transport and autoinhibition mechanisms of Vo complex. Sci Adv 6(41).
[5] Roh, SH, Hryc, CF, Jeong, HH, Fei, X, Jakana, J, Lorimer, GH, & Chiu, W (2017) Subunit conformational variation within individual GroEL oligomers resolved by Cryo-EM. Proc Natl Acad Sci U S A 114(31):8259-8264.
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Wah Chiu is the Wallenberg-Bienenstock Professor in the department of Bioengineering, department of Microbiology and Immunology and the SLAC National Accelerator Laboratory at Stanford University. Formerly, he spent three decades at Baylor College of Medicine and is a founder of the Keck Center for Quantitative Biomedical Sciences with multiple academic institutions in the Greater Houston Area. His work has made multiple transformational contributions in developing single particle electron cryo-microscopy as a tool for the structural determination of molecular machines towards atomic resolution. He has collaborated broadly with researchers around the globe on cryo-EM of viruses, chaperonins, ion channels, RNA-protein complexes and RNAs. He currently directs the NIH-designated Stanford-SLAC Cryo-EM Center, which is accessible to the global community for high resolution data collection and conducts training on cryo-EM methodology to new investigators.
