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Eng ET, Rice WJ, Cheng A, Carragher B, Potter CS. What to expect from cryo-EM (national service centers). Acta Crystallogr A Found Adv 2019. [DOI: 10.1107/s0108767319099707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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27
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Eng ET, Kopylov M, Negro CJ, Dallaykan S, Rice WJ, Jordan KD, Kelley K, Carragher B, Potter CS. Reducing cryoEM file storage using lossy image formats. J Struct Biol 2019; 207:49-55. [PMID: 31121317 DOI: 10.1016/j.jsb.2019.04.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 03/11/2019] [Accepted: 04/16/2019] [Indexed: 10/26/2022]
Abstract
Recent advances in instrumentation and software for cryoEM have increased the applicability and utility of this method. High levels of automation and faster data acquisition rates require hard decisions to be made regarding data retention. Here we investigate the efficacy of data compression applied to aligned summed movie files. Surprisingly, these images can be compressed using a standard lossy method that reduces file storage by 90-95% and yet can still be processed to provide sub-2 Å reconstructed maps. We do not advocate this as an archival method, but it may provide a useful means for retaining images as an historical record, especially at large facilities.
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Zhao L, Kopylov M, Potter CS, Carragher B, Finn MG. Engineering the PP7 Virus Capsid as a Peptide Display Platform. ACS NANO 2019; 13:4443-4454. [PMID: 30912918 PMCID: PMC6991139 DOI: 10.1021/acsnano.8b09683] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
As self-assembling polyvalent nanoscale structures that can tolerate substantial genetic and chemical modification, virus-like particles are useful in a variety of fields. Here we describe the genetic modification and structural characterization of the Leviviridae PP7 capsid protein as a platform for the presentation of functional polypeptides. This particle was shown to tolerate the display of sequences from 1 kDa (a cell penetrating peptide) to 14 kDa (the Fc-binding double Z-domain) on its exterior surface as C-terminal genetic fusions to the coat protein. In addition, a dimeric construct allowed the presentation of exogenous loops between capsid monomers and the simultaneous presentation of two different peptides at different positions on the icosahedral structure. The PP7 particle is thereby significantly more tolerant of these types of polypeptide additions than Qβ and MS2, the other Leviviridae-derived VLPs in common use.
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Brasch J, Goodman KM, Noble AJ, Rapp M, Mannepalli S, Bahna F, Dandey VP, Bepler T, Berger B, Maniatis T, Potter CS, Carragher B, Honig B, Shapiro L. Visualization of clustered protocadherin neuronal self-recognition complexes. Nature 2019; 569:280-283. [PMID: 30971825 DOI: 10.1038/s41586-019-1089-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 03/07/2019] [Indexed: 11/09/2022]
Abstract
Neurite self-recognition and avoidance are fundamental properties of all nervous systems1. These processes facilitate dendritic arborization2,3, prevent formation of autapses4 and allow free interaction among non-self neurons1,2,4,5. Avoidance among self neurites is mediated by stochastic cell-surface expression of combinations of about 60 isoforms of α-, β- and γ-clustered protocadherin that provide mammalian neurons with single-cell identities1,2,4-13. Avoidance is observed between neurons that express identical protocadherin repertoires2,5, and single-isoform differences are sufficient to prevent self-recognition10. Protocadherins form isoform-promiscuous cis dimers and isoform-specific homophilic trans dimers10,14-20. Although these interactions have previously been characterized in isolation15,17-20, structures of full-length protocadherin ectodomains have not been determined, and how these two interfaces engage in self-recognition between neuronal surfaces remains unknown. Here we determine the molecular arrangement of full-length clustered protocadherin ectodomains in single-isoform self-recognition complexes, using X-ray crystallography and cryo-electron tomography. We determine the crystal structure of the clustered protocadherin γB4 ectodomain, which reveals a zipper-like lattice that is formed by alternating cis and trans interactions. Using cryo-electron tomography, we show that clustered protocadherin γB6 ectodomains tethered to liposomes spontaneously assemble into linear arrays at membrane contact sites, in a configuration that is consistent with the assembly observed in the crystal structure. These linear assemblies pack against each other as parallel arrays to form larger two-dimensional structures between membranes. Our results suggest that the formation of ordered linear assemblies by clustered protocadherins represents the initial self-recognition step in neuronal avoidance, and thus provide support for the isoform-mismatch chain-termination model of protocadherin-mediated self-recognition, which depends on these linear chains11.
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Bobe D, Rice WJ, Eng ET, Kim LY, Kopylov M, Raczkowski AM, Carragher B, Potter CS. Single Particle Cryo-EM Workflow: Structures of Apoferritin and Aldolase. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.3080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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31
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Eng ET, Cheng A, Rice WJ, Kopylov M, Kim LY, Raczkowski AM, Bobe D, Jordan K, Kelley K, Potter CS, Carragher B. Leginon's Extended Image Shift Mode Increases the throughput for Single Particle Data Collection. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.3078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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32
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Steffes V, Zhang Z, Crowe J, MacDonald S, Ewert KK, Carragher B, Potter CS, Safinya CR. Lipid Nanomaterials for Paclitaxel Delivery in Cancer Therapeutics: Effect of Pegylation and Charge on the Morphology and Efficacy. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.2735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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33
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Noble AJ, Wei H, Dandey VP, Zhang Z, Tan YZ, Potter CS, Carragher B. Reducing effects of particle adsorption to the air-water interface in cryo-EM. Nat Methods 2018; 15:793-795. [PMID: 30250056 PMCID: PMC6168394 DOI: 10.1038/s41592-018-0139-3] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/25/2018] [Indexed: 12/31/2022]
Abstract
Most protein particles prepared in vitreous ice for single-particle cryo-electron microscopy (cryo-EM) are adsorbed to air-water or substrate-water interfaces, which can cause the particles to adopt preferred orientations. By using a rapid plunge-freezing robot and nanowire grids, we were able to reduce some of the deleterious effects of the air-water interface by decreasing the dwell time of particles in thin liquid films. We demonstrated this by using single-particle cryo-EM and cryo-electron tomography (cryo-ET) to examine hemagglutinin, insulin receptor complex, and apoferritin.
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Rice WJ, Cheng A, Noble AJ, Eng ET, Kim LY, Carragher B, Potter CS. Routine determination of ice thickness for cryo-EM grids. J Struct Biol 2018; 204:38-44. [PMID: 29981485 PMCID: PMC6119488 DOI: 10.1016/j.jsb.2018.06.007] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 06/11/2018] [Accepted: 06/27/2018] [Indexed: 12/12/2022]
Abstract
Recent advances in instrumentation and automation have made cryo-EM a popular method for producing near-atomic resolution structures of a variety of proteins and complexes. Sample preparation is still a limiting factor in collecting high quality data. Thickness of the vitreous ice in which the particles are embedded is one of the many variables that need to be optimized for collection of the highest quality data. Here we present two methods, using either an energy filter or scattering outside the objective aperture, to measure ice thickness for potentially every image collected. Unlike geometrical or tomographic methods, these can be implemented directly in the single particle collection workflow without interrupting or significantly slowing down data collection. We describe the methods as implemented into the Leginon/Appion data collection workflow, along with some examples from test cases. Routine monitoring of ice thickness should prove helpful for optimizing sample preparation, data collection, and data processing.
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Scapin G, Potter CS, Carragher B. Cryo-EM for Small Molecules Discovery, Design, Understanding, and Application. Cell Chem Biol 2018; 25:1318-1325. [PMID: 30100349 DOI: 10.1016/j.chembiol.2018.07.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 05/11/2018] [Accepted: 07/05/2018] [Indexed: 12/13/2022]
Abstract
We present a perspective of our view of the application of cryoelectron microscopy (cryo-EM) to structure-based drug design (SBDD). We discuss the basic needs and requirements for SBDD, the current state of cryo-EM, and the challenges that need to be overcome for this technique to reach its full potential in facilitating the process of drug discovery.
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Dionne G, Qiu X, Rapp M, Liang X, Zhao B, Peng G, Katsamba PS, Ahlsen G, Rubinstein R, Potter CS, Carragher B, Honig B, Müller U, Shapiro L. Mechanotransduction by PCDH15 Relies on a Novel cis-Dimeric Architecture. Neuron 2018; 99:480-492.e5. [PMID: 30057206 DOI: 10.1016/j.neuron.2018.07.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 06/06/2018] [Accepted: 06/29/2018] [Indexed: 10/28/2022]
Abstract
The tip link, a filament formed by protocadherin 15 (PCDH15) and cadherin 23, conveys mechanical force from sound waves and head movement to open hair-cell mechanotransduction channels. Tip-link cadherins are thought to have acquired structural features critical for their role in mechanotransduction. Here, we biophysically and structurally characterize the unusual cis-homodimeric architecture of PCDH15. We show that PCDH15 molecules form double-helical assemblies through cis-dimerization interfaces in the extracellular cadherin EC2-EC3 domain region and in a unique membrane-proximal domain. Electron microscopy studies visualize the cis-dimeric PCDH15 assembly and reveal the PCDH15 extracellular domain as a parallel double helix with cis cross-bridges at the two locations we defined. The helical configuration suggests the potential for elasticity through helix winding and unwinding. Functional studies in hair cells show that mutations that perturb PCDH15 dimerization contacts affect mechanotransduction. Together, these data reveal the cis-dimeric architecture of PCDH15 and show that dimerization is critical for sensing mechanical stimuli.
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Cheng A, Eng ET, Alink L, Rice WJ, Jordan KD, Kim LY, Potter CS, Carragher B. High resolution single particle cryo-electron microscopy using beam-image shift. J Struct Biol 2018; 204:270-275. [PMID: 30055234 DOI: 10.1016/j.jsb.2018.07.015] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 07/21/2018] [Accepted: 07/24/2018] [Indexed: 11/19/2022]
Abstract
Automated data acquisition is used widely for single-particle reconstruction of three-dimensional (3D) volumes of biological complexes preserved in vitreous ice and imaged in a transmission electron microscope. Automation has become integral to this method because of the very large number of particle images required in order to overcome the typically low signal-to-noise ratio of these images. For optimal efficiency, automated data acquisition software packages typically employ some beam-image shift targeting as this method is both fast and accurate (±0.1 µm). In contrast, using only stage movement, relocation to a targeted area under low-dose conditions can only be achieved in combination with multiple iterations or long relaxation times, both reducing efficiency. Nevertheless it is well known that applying beam-image shift induces beam-tilt and with it a potential structure phase error with a phase error π/4 the highest acceptable value. This theory has been used as an argument against beam-image shift for high resolution data collection. Nevertheless, in practice many small beam-image shift datasets have resulted in 3D reconstructions beyond the π/4 phase error limit. To address this apparent contradiction, we performed cryo-EM single-particle reconstructions on a T20S proteasome sample using applied beam-image shifts corresponding to beam tilts from 0 to 10 mrad. To evaluate the results we compared the FSC values, and examined the water density peaks in the 3D map. We conclude that the phase error does not limit the validity of the 3D reconstruction from single-particle averaging beyond the π/4 resolution limit.
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Scapin G, Dandey V, Zhang Z, Prosise W, Hruza A, Strickland C, Kelly T, Mayhood T, Potter CS, Carragher B. Structure of the insulin receptor in complex with insulin using single-particle cryo-EM analysis. Acta Crystallogr A Found Adv 2018. [DOI: 10.1107/s0108767318098999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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39
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Scapin G, Potter CS, Carragher B. Cryo-EM for drug discovery, design, understanding and application. Acta Crystallogr A Found Adv 2018. [DOI: 10.1107/s0108767318095648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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40
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Dingens AS, Acharya P, Haddox HK, Rawi R, Xu K, Chuang GY, Wei H, Zhang B, Mascola JR, Carragher B, Potter CS, Overbaugh J, Kwong PD, Bloom JD. Complete functional mapping of infection- and vaccine-elicited antibodies against the fusion peptide of HIV. PLoS Pathog 2018; 14:e1007159. [PMID: 29975771 PMCID: PMC6049957 DOI: 10.1371/journal.ppat.1007159] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 07/17/2018] [Accepted: 06/15/2018] [Indexed: 11/19/2022] Open
Abstract
Eliciting broadly neutralizing antibodies (bnAbs) targeting envelope (Env) is a major goal of HIV vaccine development, but cross-clade breadth from immunization has only sporadically been observed. Recently, Xu et al (2018) elicited cross-reactive neutralizing antibody responses in a variety of animal models using immunogens based on the epitope of bnAb VRC34.01. The VRC34.01 antibody, which was elicited by natural human infection, targets the N terminus of the Env fusion peptide, a critical component of the virus entry machinery. Here we precisely characterize the functional epitopes of VRC34.01 and two vaccine-elicited murine antibodies by mapping all single amino-acid mutations to the BG505 Env that affect viral neutralization. While escape from VRC34.01 occurred via mutations in both fusion peptide and distal interacting sites of the Env trimer, escape from the vaccine-elicited antibodies was mediated predominantly by mutations in the fusion peptide. Cryo-electron microscopy of four vaccine-elicited antibodies in complex with Env trimer revealed focused recognition of the fusion peptide and provided a structural basis for development of neutralization breadth. Together, these functional and structural data suggest that the breadth of vaccine-elicited antibodies targeting the fusion peptide can be enhanced by specific interactions with additional portions of Env. Thus, our complete maps of viral escape both delineate pathways of resistance to these fusion peptide-directed antibodies and provide a strategy to improve the breadth or potency of future vaccine-induced antibodies against Env’s fusion peptide. A major goal of HIV-1 vaccine design is to elicit antibodies that neutralize diverse strains of HIV-1. Recently, some of us elicited such antibodies in animal models using immunogens based on the epitope of a broad antibody (VRC34.01) isolated from an infected individual. Further improving these vaccine-elicited antibody responses will require a detailed understanding of how the resulting antibodies target HIV’s envelope protein (Env). Here, we used mutational antigenic profiling to precisely map the epitopes of two vaccine-elicited antibodies and the template VRC34.01 antibody. We did this by quantifying the effect of all possible amino acid mutations to Env on antibody neutralization. Although all antibodies target a similar region of Env, we found clear differences in the functional interaction of Env with these vaccine- and infection-elicited antibodies. We combined these functional data with structural analyses to identify antibody–Env interactions that may contribute to the relatively greater breadth of the infection-elicited antibody and could improve the breadth of vaccine-elicited antibodies. These data thereby help to refine vaccination schemes to achieve broader responses.
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41
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Kim LY, Rice WJ, Eng ET, Kopylov M, Cheng A, Raczkowski AM, Jordan KD, Bobe D, Potter CS, Carragher B. Benchmarking cryo-EM Single Particle Analysis Workflow. Front Mol Biosci 2018; 5:50. [PMID: 29951483 PMCID: PMC6009202 DOI: 10.3389/fmolb.2018.00050] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 05/08/2018] [Indexed: 11/17/2022] Open
Abstract
Cryo electron microscopy facilities running multiple instruments and serving users with varying skill levels need a robust and reliable method for benchmarking both the hardware and software components of their single particle analysis workflow. The workflow is complex, with many bottlenecks existing at the specimen preparation, data collection and image analysis steps; the samples and grid preparation can be of unpredictable quality, there are many different protocols for microscope and camera settings, and there is a myriad of software programs for analysis that can depend on dozens of settings chosen by the user. For this reason, we believe it is important to benchmark the entire workflow, using a standard sample and standard operating procedures, on a regular basis. This provides confidence that all aspects of the pipeline are capable of producing maps to high resolution. Here we describe benchmarking procedures using a test sample, rabbit muscle aldolase.
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Xu K, Acharya P, Kong R, Cheng C, Chuang GY, Liu K, Louder MK, O'Dell S, Rawi R, Sastry M, Shen CH, Zhang B, Zhou T, Asokan M, Bailer RT, Chambers M, Chen X, Choi CW, Dandey VP, Doria-Rose NA, Druz A, Eng ET, Farney SK, Foulds KE, Geng H, Georgiev IS, Gorman J, Hill KR, Jafari AJ, Kwon YD, Lai YT, Lemmin T, McKee K, Ohr TY, Ou L, Peng D, Rowshan AP, Sheng Z, Todd JP, Tsybovsky Y, Viox EG, Wang Y, Wei H, Yang Y, Zhou AF, Chen R, Yang L, Scorpio DG, McDermott AB, Shapiro L, Carragher B, Potter CS, Mascola JR, Kwong PD. Epitope-based vaccine design yields fusion peptide-directed antibodies that neutralize diverse strains of HIV-1. Nat Med 2018; 24:857-867. [PMID: 29867235 PMCID: PMC6358635 DOI: 10.1038/s41591-018-0042-6] [Citation(s) in RCA: 200] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/19/2018] [Indexed: 12/12/2022]
Abstract
A central goal of HIV-1 vaccine research is the elicitation of antibodies capable of neutralizing diverse primary isolates of HIV-1. Here we show that focusing the immune response to exposed N-terminal residues of the fusion peptide, a critical component of the viral entry machinery and the epitope of antibodies elicited by HIV-1 infection, through immunization with fusion peptide-coupled carriers and prefusion stabilized envelope trimers, induces cross-clade neutralizing responses. In mice, these immunogens elicited monoclonal antibodies capable of neutralizing up to 31% of a cross-clade panel of 208 HIV-1 strains. Crystal and cryoelectron microscopy structures of these antibodies revealed fusion peptide conformational diversity as a molecular explanation for the cross-clade neutralization. Immunization of guinea pigs and rhesus macaques induced similarly broad fusion peptide-directed neutralizing responses, suggesting translatability. The N terminus of the HIV-1 fusion peptide is thus a promising target of vaccine efforts aimed at eliciting broadly neutralizing antibodies.
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Noble AJ, Dandey VP, Wei H, Brasch J, Chase J, Acharya P, Tan YZ, Zhang Z, Kim LY, Scapin G, Rapp M, Eng ET, Rice WJ, Cheng A, Negro CJ, Shapiro L, Kwong PD, Jeruzalmi D, des Georges A, Potter CS, Carragher B. Routine single particle CryoEM sample and grid characterization by tomography. eLife 2018; 7:e34257. [PMID: 29809143 PMCID: PMC5999397 DOI: 10.7554/elife.34257] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 05/17/2018] [Indexed: 12/11/2022] Open
Abstract
Single particle cryo-electron microscopy (cryoEM) is often performed under the assumption that particles are not adsorbed to the air-water interfaces and in thin, vitreous ice. In this study, we performed fiducial-less tomography on over 50 different cryoEM grid/sample preparations to determine the particle distribution within the ice and the overall geometry of the ice in grid holes. Surprisingly, by studying particles in holes in 3D from over 1000 tomograms, we have determined that the vast majority of particles (approximately 90%) are adsorbed to an air-water interface. The implications of this observation are wide-ranging, with potential ramifications regarding protein denaturation, conformational change, and preferred orientation. We also show that fiducial-less cryo-electron tomography on single particle grids may be used to determine ice thickness, optimal single particle collection areas and strategies, particle heterogeneity, and de novo models for template picking and single particle alignment.
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Zhang Z, Liang WG, Bailey LJ, Tan YZ, Wei H, Wang A, Farcasanu M, Woods VA, McCord LA, Lee D, Shang W, Deprez-Poulain R, Deprez B, Liu DR, Koide A, Koide S, Kossiakoff AA, Li S, Carragher B, Potter CS, Tang WJ. Ensemble cryoEM elucidates the mechanism of insulin capture and degradation by human insulin degrading enzyme. eLife 2018; 7:33572. [PMID: 29596046 PMCID: PMC5910022 DOI: 10.7554/elife.33572] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 03/28/2018] [Indexed: 11/29/2022] Open
Abstract
Insulin degrading enzyme (IDE) plays key roles in degrading peptides vital in type two diabetes, Alzheimer's, inflammation, and other human diseases. However, the process through which IDE recognizes peptides that tend to form amyloid fibrils remained unsolved. We used cryoEM to understand both the apo- and insulin-bound dimeric IDE states, revealing that IDE displays a large opening between the homologous ~55 kDa N- and C-terminal halves to allow selective substrate capture based on size and charge complementarity. We also used cryoEM, X-ray crystallography, SAXS, and HDX-MS to elucidate the molecular basis of how amyloidogenic peptides stabilize the disordered IDE catalytic cleft, thereby inducing selective degradation by substrate-assisted catalysis. Furthermore, our insulin-bound IDE structures explain how IDE processively degrades insulin by stochastically cutting either chain without breaking disulfide bonds. Together, our studies provide a mechanism for how IDE selectively degrades amyloidogenic peptides and offers structural insights for developing IDE-based therapies.
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Scapin G, Dandey VP, Zhang Z, Prosise W, Hruza A, Kelly T, Mayhood T, Strickland C, Potter CS, Carragher B. Structure of the insulin receptor-insulin complex by single-particle cryo-EM analysis. Nature 2018; 556:122-125. [PMID: 29512653 PMCID: PMC5886813 DOI: 10.1038/nature26153] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 02/20/2018] [Indexed: 01/04/2023]
Abstract
The insulin receptor (IR) is a dimeric protein that plays a crucial role in controlling glucose homeostasis, regulating lipid, protein and carbohydrate metabolism, and modulating brain neurotransmitter levels1,2. IR dysfunctions have been associated with many diseases, including diabetes, cancer, and Alzheimer’s1,3,4. The primary sequence has been known since the 1980s5, and is composed of an extracellular portion (ectodomain, ECD), a single transmembrane helix and an intracellular tyrosine kinase domain. Insulin binding to the dimeric ECD triggers kinase domain auto-phosphorylation and subsequent activation of downstream signaling molecules. Biochemical and mutagenesis data have identified two putative insulin binding sites (S1 and S2)6. While insulin bound to an ECD fragment containing S1 and the apo ectodomain have been characterized structurally7,8, details of insulin binding to the full receptor and the signal propagation mechanism are still not understood. Here we report single particle cryoEM reconstructions for the 1:2 (4.3 Å) and 1:1 (7.4 Å) IR ECD dimer:Insulin complexes. The symmetric 4.3 Å structure shows two insulin molecules per dimer, each bound between the Leucine-rich sub domain L1 of one monomer and the first fibronectin-like domain (FnIII-1) of the other monomer, and making extensive interactions with the α subunit C-terminal helix (α-CT helix). The 7.4 Å structure has only one similarly bound insulin per receptor dimer. The structures confirm the S1 binding interactions and define the full S2 binding site. These insulin receptor states suggest that recruitment of the α-CT helix upon binding of the first insulin changes the relative sub domain orientations and triggers downstream signal propagation.
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Raczkowski AM, Eng ET, Rice WJ, Dallakyan S, Negro C, Kim LY, Jordan KD, Carragher B, Potter CS. Standardizing the Focused Ion Beam-SEM Workflow as a Tool for Versatile Imaging of Cellular Structures. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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47
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Dandey VP, Wei H, Zhang Z, Eng ET, Noble A, Rice WJ, Raczkowski A, Carragher B, Potter CS. Spotiton: a new method for vitrifying samples for cryo-EM. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s2053273317082808] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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48
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Baldwin PR, Tan YZ, Eng ET, Rice WJ, Noble AJ, Negro CJ, Cianfrocco MA, Potter CS, Carragher B. Big data in cryoEM: automated collection, processing and accessibility of EM data. Curr Opin Microbiol 2017; 43:1-8. [PMID: 29100109 DOI: 10.1016/j.mib.2017.10.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 09/27/2017] [Accepted: 10/09/2017] [Indexed: 11/24/2022]
Abstract
The scope and complexity of cryogenic electron microscopy (cryoEM) data has greatly increased, and will continue to do so, due to recent and ongoing technical breakthroughs that have led to much improved resolutions for macromolecular structures solved using this method. This big data explosion includes single particle data as well as tomographic tilt series, both generally acquired as direct detector movies of ∼10-100 frames per image or per tilt-series. We provide a brief survey of the developments leading to the current status, and describe existing cryoEM pipelines, with an emphasis on the scope of data acquisition, methods for automation, and use of cloud storage and computing.
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Liu Q, Acharya P, Dolan MA, Zhang P, Guzzo C, Lu J, Kwon A, Gururani D, Miao H, Bylund T, Chuang GY, Druz A, Zhou T, Rice WJ, Wigge C, Carragher B, Potter CS, Kwong PD, Lusso P. Quaternary contact in the initial interaction of CD4 with the HIV-1 envelope trimer. Nat Struct Mol Biol 2017; 24:370-378. [PMID: 28218750 DOI: 10.1038/nsmb.3382] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 01/25/2017] [Indexed: 12/19/2022]
Abstract
Binding of the gp120 envelope (Env) glycoprotein to the CD4 receptor is the first step in the HIV-1 infectious cycle. Although the CD4-binding site has been extensively characterized, the initial receptor interaction has been difficult to study because of major CD4-induced structural rearrangements. Here we used cryogenic electron microscopy (cryo-EM) to visualize the initial contact of CD4 with the HIV-1 Env trimer at 6.8-Å resolution. A single CD4 molecule is embraced by a quaternary HIV-1-Env surface formed by coalescence of the previously defined CD4-contact region with a second CD4-binding site (CD4-BS2) in the inner domain of a neighboring gp120 protomer. Disruption of CD4-BS2 destabilized CD4-trimer interaction and abrogated HIV-1 infectivity by preventing the acquisition of coreceptor-binding competence. A corresponding reduction in HIV-1 infectivity occurred after the mutation of CD4 residues that interact with CD4-BS2. Our results document the critical role of quaternary interactions in the initial HIV-Env-receptor contact, with implications for treatment and vaccine design.
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Eng ET, Raczkowski AM, Rice WJ, Jordan KD, Noble AJ, Cheng A, Carragher BO, Potter CS. Focused Ion Beam-Sem as a Tool for Versatile Quantitative Imaging of Cellular Structures. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.3104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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