scholarly journals In situ cryo-ET structure of phycobilisome–photosystem II supercomplex from red alga

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Meijing Li ◽  
Jianfei Ma ◽  
Xueming Li ◽  
Sen-Fang Sui
Keyword(s):  
Photosystem Ii ◽  
Structural Information ◽  
Electron Tomography ◽  
Light Energy ◽  
Porphyridium Purpureum ◽  
Cellular Environment ◽  
Interaction Interface ◽  
Subtomogram Averaging ◽  
Light Harvesting Antenna

Phycobilisome (PBS) is the main light-harvesting antenna in cyanobacteria and red algae. How PBS transfers the light energy to photosystem II (PSII) remains to be elucidated. Here we report the in situ structure of the PBS–PSII supercomplex from Porphyridium purpureum UTEX 2757 using cryo-electron tomography and subtomogram averaging. Our work reveals the organized network of hemiellipsoidal PBS with PSII on the thylakoid membrane in the native cellular environment. In the PBS–PSII supercomplex, each PBS interacts with six PSII monomers, of which four directly bind to the PBS, and two bind indirectly. Additional three ‘connector’ proteins also contribute to the connections between PBS and PSIIs. Two PsbO subunits from adjacent PSII dimers bind with each other, which may promote stabilization of the PBS–PSII supercomplex. By analyzing the interaction interface between PBS and PSII, we reveal that αLCM and ApcD connect with CP43 of PSII monomer and that αLCM also interacts with CP47' of the neighboring PSII monomer, suggesting the multiple light energy delivery pathways. The in situ structures illustrate the coupling pattern of PBS and PSII and the arrangement of the PBS–PSII supercomplex on the thylakoid, providing the near-native 3D structural information of the various energy transfer from PBS to PSII.

scholarly journals Proteasomes tether to two distinct sites at the nuclear pore complex

2017 ◽  
Vol 114 (52) ◽  
pp. 13726-13731 ◽  
Author(s):  
Sahradha Albert ◽  
Miroslava Schaffer ◽  
Florian Beck ◽  
Shyamal Mosalaganti ◽  
Shoh Asano ◽  
...  
Keyword(s):  
Nuclear Pore Complex ◽  
Binding Sites ◽  
Electron Tomography ◽  
Nuclear Pore ◽  
Cellular Environment ◽  
Subtomogram Averaging ◽  
Substrate Processing ◽  
Cellular Components ◽  
Transport Of Macromolecules

The partitioning of cellular components between the nucleus and cytoplasm is the defining feature of eukaryotic life. The nuclear pore complex (NPC) selectively gates the transport of macromolecules between these compartments, but it is unknown whether surveillance mechanisms exist to reinforce this function. By leveraging in situ cryo-electron tomography to image the native cellular environment of Chlamydomonas reinhardtii, we observed that nuclear 26S proteasomes crowd around NPCs. Through a combination of subtomogram averaging and nanometer-precision localization, we identified two classes of proteasomes tethered via their Rpn9 subunits to two specific NPC locations: binding sites on the NPC basket that reflect its eightfold symmetry and more abundant binding sites at the inner nuclear membrane that encircle the NPC. These basket-tethered and membrane-tethered proteasomes, which have similar substrate-processing state frequencies as proteasomes elsewhere in the cell, are ideally positioned to regulate transcription and perform quality control of both soluble and membrane proteins transiting the NPC.

scholarly journals The in situ structure of Parkinson’s disease-linked LRRK2

2019 ◽  
Author(s):  
Reika Watanabe ◽  
Robert Buschauer ◽  
Jan Böhning ◽  
Martina Audagnotto ◽  
Keren Lasker ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Electron Tomography ◽  
Double Helix ◽  
Pathogenic Mutation ◽  
Left Handed ◽  
Cellular Environment ◽  
Cryo Electron Tomography ◽  
Subtomogram Averaging

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most frequent cause of familial Parkinson’s disease. LRRK2 is a multi-domain protein containing a kinase and GTPase. Using in situ cryo-electron tomography and subtomogram averaging, we reveal a 14-Å structure of LRRK2 bearing a pathogenic mutation that oligomerizes as a right-handed double-helix around microtubules, which are left-handed. Using integrative modeling, we determine the architecture of LRRK2, showing that the GTPase points towards the microtubule, while the kinase is exposed to the cytoplasm. We identify two oligomerization interfaces mediated by non-catalytic domains. Mutation of one of these abolishes LRRK2 microtubule-association. Our work demonstrates the power of cryo-electron tomography to obtain structures of previously unsolved proteins in their cellular environment and provides insights into LRRK2 function and pathogenicity.

scholarly journals In situ structural analysis of Golgi intracisternal protein arrays

2015 ◽  
Vol 112 (36) ◽  
pp. 11264-11269 ◽  
Author(s):  
Benjamin D. Engel ◽  
Miroslava Schaffer ◽  
Sahradha Albert ◽  
Shoh Asano ◽  
Jürgen M. Plitzko ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Electron Tomography ◽  
Ion Beam ◽  
Asymmetric Membrane ◽  
Protein Arrays ◽  
Cellular Environment ◽  
Filament Bundles ◽  
Subtomogram Averaging ◽  
And Function

We acquired molecular-resolution structures of the Golgi within its native cellular environment. Vitreous Chlamydomonas cells were thinned by cryo-focused ion beam milling and then visualized by cryo-electron tomography. These tomograms revealed structures within the Golgi cisternae that have not been seen before. Narrow trans-Golgi lumina were spanned by asymmetric membrane-associated protein arrays that had ∼6-nm lateral periodicity. Subtomogram averaging showed that the arrays may determine the narrow central spacing of the trans-Golgi cisternae through zipper-like interactions, thereby forcing cargo to the trans-Golgi periphery. Additionally, we observed dense granular aggregates within cisternae and intracisternal filament bundles associated with trans-Golgi buds. These native in situ structures provide new molecular insights into Golgi architecture and function.

scholarly journals A guided approach for subtomogram averaging of challenging macromolecular assemblies

2020 ◽  
Author(s):  
Danielle Grotjahn ◽  
Saikat Chowdhury ◽  
Gabriel C. Lander
Keyword(s):  
Electron Tomography ◽  
A Priori ◽  
Three Dimensional ◽  
Structural Heterogeneity ◽  
Dimensional Structure ◽  
Diverse Range ◽  
Macromolecular Assemblies ◽  
Cryo Electron Tomography ◽  
Subtomogram Averaging

AbstractCryo-electron tomography is a powerful biophysical technique enabling three-dimensional visualization of complex biological systems. Macromolecular targets of interest identified within cryo-tomograms can be computationally extracted, aligned, and averaged to produce a better-resolved structure through a process called subtomogram averaging (STA). However, accurate alignment of macromolecular machines that exhibit extreme structural heterogeneity and conformational flexibility remains a significant challenge with conventional STA approaches. To expand the applicability of STA to a broader range of pleomorphic complexes, we developed a user-guided, focused refinement approach that can be incorporated into the standard STA workflow to facilitate the robust alignment of particularly challenging samples. We demonstrate that it is possible to align visually recognizable portions of multi-subunit complexes by providing a priori information regarding their relative orientations within cryo-tomograms, and describe how this strategy was applied to successfully elucidate the first three-dimensional structure of the dynein-dynactin motor protein complex bound to microtubules. Our approach expands the application of STA for solving a more diverse range of heterogeneous biological structures, and establishes a conceptual framework for the development of automated strategies to deconvolve the complexity of crowded cellular environments and improve in situ structure determination technologies.

scholarly journals Automated cryo-lamella preparation for high-throughput in-situ structural biology

2019 ◽  
Author(s):  
Genevieve Buckley ◽  
Gediminas Gervinskas ◽  
Cyntia Taveneau ◽  
Hari Venugopal ◽  
James C. Whisstock ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Structural Biology ◽  
Focused Ion Beam ◽  
Electron Tomography ◽  
Ion Beam ◽  
Automated Method ◽  
Cellular Environment ◽  
Transmission Electron

AbstractCryo-transmission electron tomography (cryo-ET) in association with cryo-focused ion beam (cryo-FIB) milling enables structural biology studies to be performed directly within the cellular environment. Cryo-preserved cells are milled and a lamella with a thickness of 200-300 nm provides an electron transparent window suitable for cryo-ET imaging. Cryo-FIB milling is an effective method, but it is a tedious and time-consuming process, which typically results in ~10 lamellae per day. Here, we introduce an automated method to reproducibly prepare cryo-lamellae on a grid and reduce the amount of human supervision. We tested the routine on cryo-preserved Saccharomyces cerevisiae and demonstrate that this method allows an increased throughput, achieving a rate of 5 lamellae/hour without the need to supervise the FIB milling. We demonstrate that the quality of the lamellae is consistent throughout the preparation and their compatibility with cryo-ET analyses.

scholarly journals The structure of the COPI coat determined within the cell

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Yury S Bykov ◽  
Miroslava Schaffer ◽  
Svetlana O Dodonova ◽  
Sahradha Albert ◽  
Jürgen M Plitzko ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Structural Model ◽  
Electron Tomography ◽  
Ion Beam ◽  
Membrane Thickness ◽  
In Vitro Reconstitution ◽  
Cryo Electron Tomography ◽  
Subtomogram Averaging

COPI-coated vesicles mediate trafficking within the Golgi apparatus and from the Golgi to the endoplasmic reticulum. The structures of membrane protein coats, including COPI, have been extensively studied with in vitro reconstitution systems using purified components. Previously we have determined a complete structural model of the in vitro reconstituted COPI coat (Dodonova et al., 2017). Here, we applied cryo-focused ion beam milling, cryo-electron tomography and subtomogram averaging to determine the native structure of the COPI coat within vitrified Chlamydomonas reinhardtii cells. The native algal structure resembles the in vitro mammalian structure, but additionally reveals cargo bound beneath β’–COP. We find that all coat components disassemble simultaneously and relatively rapidly after budding. Structural analysis in situ, maintaining Golgi topology, shows that vesicles change their size, membrane thickness, and cargo content as they progress from cis to trans, but the structure of the coat machinery remains constant.

scholarly journals In-cell structures of a conserved supramolecular array at the mitochondria-cytoskeleton interface in mammalian sperm

2021 ◽  
Author(s):  
Miguel Ricardo Leung ◽  
Riccardo Zenezini Chiozzi ◽  
Marc C. Roelofs ◽  
Johannes F. Hevler ◽  
Ravi Teja Ravi ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Structural Information ◽  
Electron Tomography ◽  
Ion Beam ◽  
Mammalian Species ◽  
Cell Types ◽  
Mammalian Sperm ◽  
Cell Structures ◽  
Voltage Dependent ◽  
Subtomogram Averaging

SummaryMitochondria-cytoskeleton interactions modulate cellular physiology by regulating mitochondrial transport, positioning, and immobilization. However, there is very little structural information defining mitochondria-cytoskeleton interfaces in any cell type. Here, we use cryo-focused ion beam milling-enabled cryo-electron tomography to image mammalian sperm, where mitochondria wrap around the ciliary cytoskeleton. We find that mitochondria are tethered to their neighbors through inter-mitochondrial linkers and are anchored to the cytoskeleton through ordered arrays on the outer mitochondrial membrane. We use subtomogram averaging to resolve in-cell structures of these arrays from three mammalian species, revealing they are conserved across species despite variations in mitochondrial dimensions and cristae organization. We find that the arrays consist of boat-shaped particles anchored on a network of membrane pores whose arrangement and dimensions are consistent with voltage dependent anion channels. Proteomics and in-cell cross-linking mass spectrometry suggest that the conserved arrays are composed of glycerol kinase-like proteins. Ordered supramolecular assemblies may serve to stabilize similar contact sites in other cell types where mitochondria need to be immobilized in specific subcellular environments, such as in muscles and neurons.

scholarly journals A flexible framework for multi-particle refinement in cryo-electron tomography

PLoS Biology ◽  
2021 ◽  
Vol 19 (8) ◽  
pp. e3001319
Author(s):  
Alister Burt ◽  
Lorenzo Gaifas ◽  
Tom Dendooven ◽  
Irina Gutsche
Keyword(s):  
Software Package ◽  
Electron Tomography ◽  
Macromolecular Structure ◽  
Computational Tools ◽  
Cryo Electron Tomography ◽  
Flexible Framework ◽  
Subtomogram Averaging ◽  
Particle Refinement ◽  
Hiv 1

Cryo-electron tomography (cryo-ET) and subtomogram averaging (STA) are increasingly used for macromolecular structure determination in situ. Here, we introduce a set of computational tools and resources designed to enable flexible approaches to STA through increased automation and simplified metadata handling. We create a bidirectional interface between the Dynamo software package and the Warp-Relion-M pipeline, providing a framework for ab initio and geometrical approaches to multiparticle refinement in M. We illustrate the power of working within this framework by applying it to EMPIAR-10164, a publicly available dataset containing immature HIV-1 virus-like particles (VLPs), and a challenging in situ dataset containing chemosensory arrays in bacterial minicells. Additionally, we provide a comprehensive, step-by-step guide to obtaining a 3.4-Å reconstruction from EMPIAR-10164. The guide is hosted on https://teamtomo.org/, a collaborative online platform we establish for sharing knowledge about cryo-ET.

scholarly journals In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges

2020 ◽  
Author(s):  
Beata Turoňová ◽  
Mateusz Sikora ◽  
Christoph Schürmann ◽  
Wim J. H. Hagen ◽  
Sonja Welsch ◽  
...  
Keyword(s):  
Large Scale ◽  
Vaccine Development ◽  
Electron Tomography ◽  
Structural Features ◽  
Globular Domain ◽  
Data Set ◽  
Host Cell Surface ◽  
Subtomogram Averaging ◽  
Dynamics Simulations

AbstractThe spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is required for cell entry and is the major focus for vaccine development. We combine cryo electron tomography, subtomogram averaging and molecular dynamics simulations to structurally analyze S in situ. Compared to recombinant S, the viral S is more heavily glycosylated and occurs predominantly in a closed pre-fusion conformation. We show that the stalk domain of S contains three hinges that give the globular domain unexpected orientational freedom. We propose that the hinges allow S to scan the host cell surface, shielded from antibodies by an extensive glycan coat. The structure of native S contributes to our understanding of SARS-CoV-2 infection and the development of safe vaccines. The large scale tomography data set of SARS-CoV-2 used for this study is therefore sufficient to resolve structural features to below 5 Ångstrom, and is publicly available at EMPIAR-10453.

scholarly journals The elusive actin cytoskeleton of a green alga expressing both conventional and divergent actins

2019 ◽  
Vol 30 (22) ◽  
pp. 2827-2837 ◽  
Author(s):  
Evan W. Craig ◽  
David M. Mueller ◽  
Brae M. Bigge ◽  
Miroslava Schaffer ◽  
Benjamin D. Engel ◽  
...  
Keyword(s):  
Green Alga ◽  
Actin Filaments ◽  
Electron Tomography ◽  
Filamentous Actin ◽  
Cellular Processes ◽  
Cellular Environment ◽  
Actin Structure ◽  
Actin Isoform ◽  
Labeling Method

The green alga Chlamydomonas reinhardtii is a leading model system to study photosynthesis, cilia, and the generation of biological products. The cytoskeleton plays important roles in all of these cellular processes, but to date, the filamentous actin network within Chlamydomonas has remained elusive. By optimizing labeling conditions, we can now visualize distinct linear actin filaments at the posterior of the nucleus in both live and fixed vegetative cells. Using in situ cryo-electron tomography, we confirmed this localization by directly imaging actin filaments within the native cellular environment. The fluorescently labeled structures are sensitive to the depolymerizing agent latrunculin B (Lat B), demonstrating the specificity of our optimized labeling method. Interestingly, Lat B treatment resulted in the formation of a transient ring-like filamentous actin structure around the nucleus. The assembly of this perinuclear ring is dependent upon a second actin isoform, NAP1, which is strongly up-regulated upon Lat B treatment and is insensitive to Lat B–induced depolymerization. Our study combines orthogonal strategies to provide the first detailed visual characterization of filamentous actins in Chlamydomonas, allowing insights into the coordinated functions of two actin isoforms expressed within the same cell.

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