scholarly journals Single-particle cryo-EM structure of a voltage-activated potassium channel in lipid nanodiscs

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Doreen Matthies ◽  
Chanhyung Bae ◽  
Gilman ES Toombes ◽  
Tara Fox ◽  
Alberto Bartesaghi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Lipid Bilayer ◽  
Single Particle ◽  
Transmembrane Domain ◽  
X Ray ◽  
Kv Channels ◽  
Cryo Electron Microscopy ◽  
Transmembrane Voltage ◽  
Structural Mechanisms ◽  
Lipid Nanodiscs

Voltage-activated potassium (Kv) channels open to conduct K+ ions in response to membrane depolarization, and subsequently enter non-conducting states through distinct mechanisms of inactivation. X-ray structures of detergent-solubilized Kv channels appear to have captured an open state even though a non-conducting C-type inactivated state would predominate in membranes in the absence of a transmembrane voltage. However, structures for a voltage-activated ion channel in a lipid bilayer environment have not yet been reported. Here we report the structure of the Kv1.2–2.1 paddle chimera channel reconstituted into lipid nanodiscs using single-particle cryo-electron microscopy. At a resolution of ~3 Å for the cytosolic domain and ~4 Å for the transmembrane domain, the structure determined in nanodiscs is similar to the previously determined X-ray structure. Our findings show that large differences in structure between detergent and lipid bilayer environments are unlikely, and enable us to propose possible structural mechanisms for C-type inactivation.

Uncovering the structures of modular polyketide synthases

2015 ◽  
Vol 32 (3) ◽  
pp. 436-453 ◽  
Author(s):  
Kira J. Weissman
Keyword(s):  
Electron Microscopy ◽  
Structural Biology ◽  
Structural Characterization ◽  
Small Angle ◽  
Single Particle ◽  
Polyketide Synthases ◽  
X Ray ◽  
X Ray Scattering ◽  
Cryo Electron Microscopy

This review covers a breakthrough in the structural biology of the gigantic modular polyketide synthases (PKS): the structural characterization of intact modules by single-particle cryo-electron microscopy and small-angle X-ray scattering.

scholarly journals Structure of the human epithelial sodium channel by cryo-electron microscopy

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Sigrid Noreng ◽  
Arpita Bharadwaj ◽  
Richard Posert ◽  
Craig Yoshioka ◽  
Isabelle Baconguis
Keyword(s):  
Electron Microscopy ◽  
Ion Channel ◽  
Sodium Channel ◽  
Conformational Changes ◽  
Single Particle ◽  
Transmembrane Domain ◽  
Epithelial Sodium Channel ◽  
Cryo Electron Microscopy ◽  
Inhibitory Domain ◽  
Epithelial Sodium Channel Enac

The epithelial sodium channel (ENaC), a member of the ENaC/DEG superfamily, regulates Na+ and water homeostasis. ENaCs assemble as heterotrimeric channels that harbor protease-sensitive domains critical for gating the channel. Here, we present the structure of human ENaC in the uncleaved state determined by single-particle cryo-electron microscopy. The ion channel is composed of a large extracellular domain and a narrow transmembrane domain. The structure reveals that ENaC assembles with a 1:1:1 stoichiometry of α:β:γ subunits arranged in a counter-clockwise manner. The shape of each subunit is reminiscent of a hand with key gating domains of a ‘finger’ and a ‘thumb.’ Wedged between these domains is the elusive protease-sensitive inhibitory domain poised to regulate conformational changes of the ‘finger’ and ‘thumb’; thus, the structure provides the first view of the architecture of inhibition of ENaC.

scholarly journals Structure Determination by Single-Particle Cryo-Electron Microscopy: Only the Sky (and Intrinsic Disorder) is the Limit

2019 ◽  
Vol 20 (17) ◽  
pp. 4186 ◽  
Author(s):  
Emeka Nwanochie ◽  
Vladimir N. Uversky
Keyword(s):  
Electron Microscopy ◽  
Nmr Spectroscopy ◽  
Structure Determination ◽  
Single Particle ◽  
Protein Structures ◽  
X Ray ◽  
X Ray Crystallography ◽  
Intrinsically Disordered ◽  
Small Proteins ◽  
Cryo Electron Microscopy

Traditionally, X-ray crystallography and NMR spectroscopy represent major workhorses of structural biologists, with the lion share of protein structures reported in protein data bank (PDB) being generated by these powerful techniques. Despite their wide utilization in protein structure determination, these two techniques have logical limitations, with X-ray crystallography being unsuitable for the analysis of highly dynamic structures and with NMR spectroscopy being restricted to the analysis of relatively small proteins. In recent years, we have witnessed an explosive development of the techniques based on Cryo-electron microscopy (Cryo-EM) for structural characterization of biological molecules. In fact, single-particle Cryo-EM is a special niche as it is a technique of choice for the structural analysis of large, structurally heterogeneous, and dynamic complexes. Here, sub-nanometer atomic resolution can be achieved (i.e., resolution below 10 Å) via single-particle imaging of non-crystalline specimens, with accurate 3D reconstruction being generated based on the computational averaging of multiple 2D projection images of the same particle that was frozen rapidly in solution. We provide here a brief overview of single-particle Cryo-EM and show how Cryo-EM has revolutionized structural investigations of membrane proteins. We also show that the presence of intrinsically disordered or flexible regions in a target protein represents one of the major limitations of this promising technique.

scholarly journals Conformations of macromolecules and their complexes from heterogeneous datasets

2014 ◽  
Vol 369 (1647) ◽  
pp. 20130567 ◽  
Author(s):  
P. Schwander ◽  
R. Fung ◽  
A. Ourmazd
Keyword(s):  
Electron Microscopy ◽  
Prior Knowledge ◽  
Single Particle ◽  
Conformational Heterogeneity ◽  
X Ray ◽  
Cryo Electron Microscopy ◽  
Heterogeneous Datasets ◽  
Large Ensembles ◽  
New Generation ◽  
Image Datasets

We describe a new generation of algorithms capable of mapping the structure and conformations of macromolecules and their complexes from large ensembles of heterogeneous snapshots, and demonstrate the feasibility of determining both discrete and continuous macromolecular conformational spectra. These algorithms naturally incorporate conformational heterogeneity without resort to sorting and classification, or prior knowledge of the type of heterogeneity present. They are applicable to single-particle diffraction and image datasets produced by X-ray lasers and cryo-electron microscopy, respectively, and particularly suitable for systems not easily amenable to purification or crystallization.

scholarly journals qFit 3: Protein and ligand multiconformer modeling for X-ray crystallographic and single-particle cryo-EM density maps

2020 ◽  
Author(s):  
Blake T. Riley ◽  
Stephanie A. Wankowicz ◽  
Saulo H. P. de Oliveira ◽  
Gydo C. P. van Zundert ◽  
Daniel Hogan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Single Particle ◽  
Structural Data ◽  
Conformational Ensemble ◽  
Distributed Application ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cryo Electron Microscopy ◽  
Formidable Challenge ◽  
Density Maps

AbstractNew X-ray crystallography and cryo-electron microscopy (cryo-EM) approaches yield vast amounts of structural data from dynamic proteins and their complexes. Modeling the full conformational ensemble can provide important biological insights, but identifying and modeling an internally consistent set of alternate conformations remains a formidable challenge. qFit efficiently automates this process by generating a parsimonious multiconformer model. We refactored qFit from a distributed application into software that runs efficiently on a small server, desktop, or laptop. We describe the new qFit 3 software and provide some examples. qFit 3 is open-source under the MIT license, and is available at https://github.com/ExcitedStates/qfit-3.0.

scholarly journals Single-particle cryo-EM—How did it get here and where will it go

Science ◽  
2018 ◽  
Vol 361 (6405) ◽  
pp. 876-880 ◽  
Author(s):  
Yifan Cheng
Keyword(s):  
Electron Microscopy ◽  
Structural Biology ◽  
Single Particle ◽  
Electron Crystallography ◽  
The Past ◽  
Cryo Electron Microscopy ◽  
Technological Advances ◽  
The Future ◽  
Electron Cryotomography

Cryo–electron microscopy, or simply cryo-EM, refers mainly to three very different yet closely related techniques: electron crystallography, single-particle cryo-EM, and electron cryotomography. In the past few years, single-particle cryo-EM in particular has triggered a revolution in structural biology and has become a newly dominant discipline. This Review examines the fascinating story of its start and evolution over the past 40-plus years, delves into how and why the recent technological advances have been so groundbreaking, and briefly considers where the technique may be headed in the future.

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.

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