Biology subjects

Sachse, C.

Publications and source records attributed to Sachse, C..

At least 19 recordsLinked to original sources

bioRxiv2026

In situ visualization of autophagy suggests vesicle fusion can contribute to phagophore expansion

The autophagy core machinery mediates the enclosure of cytosolic cargo destined for degradation in the lysosome. The Atg9-Atg2-Atg18 complex coordinates phagophore expansion via directed lipid transfer until closure of the phagophore rim. Using an Atg2 variant (Atg2-PM4) as a model of decelerated autophagosome biogenesis, we visualized the morphological states prior to autophagosome closure by cryogenic correlative light and electron microscopy in S. cerevisiae. Using in situ cryo-electron tomography, we find an enlarged rim morphology of an expanding phagophore in Atg2-PM4 cells in comparison with Atg2 wildtype condition. Analysis of segmented rim membrane features as well as surrounding and attached vesicles suggest that the enlarged rims are a result of cytosolic vesicles fusing with the growing phagophore. High-resolution imaging in this study shows that, apart from the initial nucleation phase, vesicle fusion can also contribute to phagophore expansion during later stages of autophagosome biogenesis.

cell biology↗

bioRxiv2026

Rejuvenation of the Aged Cerebrovascular System via Protein Corona-Guided Fusogenic Liposome Delivery

Brain vascular aging is increasingly recognized as a critical therapeutic target for age-related cognitive decline. Oxidative stress, bioenergetic dysfunction, and molecular damage play central roles in the progression of vascular aging, contributing to cerebrovascular dysfunction and impaired cognitive function. While naturally occurring polyphenols such as resveratrol (RSV) have demonstrated potential in mitigating aging-related pathologies, their poor bioavailability and limited brain targeting efficiency significantly constrain their therapeutic impact. As a result, high doses or advanced drug delivery strategies are necessary to achieve meaningful physiological effects. We introduce a novel nanocarrier system designed to enhance RSV delivery to the cerebral endothelium by leveraging the natural formation of an apolipoprotein E (ApoE)-enriched protein corona around fusogenic liposomes (FL) in vivo. These nanoparticles directly fuse with cytoplasmic cell membranes and thus evade endocytosis. We found that once in the circulation FL spontaneously acquire a protein corona, which is highly enriched in ApoE, a key ligand for brain endothelial low-density lipoprotein receptors (LDLR). Based on this observation, we engineered an ApoE-functionalized protein corona around FL (ApoE-FL) to systematically evaluate whether this mechanism could be exploited for targeted brain delivery. Following optimization and physicochemical characterization, the RSV-loaded liposomes were evaluated in vitro using human cerebral microvascular endothelial cells and in vivo C57BL/6 aged mice to assess their therapeutic potential. Both FL and engineered ApoE-FL liposomal delivery systems exhibited a strong affinity for endothelial cell membranes in vitro. The knockdown of the ApoE receptor, low-density lipoprotein receptor-related protein 1 (LRP1), significantly reduced liposomal docking. Microscopy analysis revealed that both ApoE-FL and non-functionalized FL directly fused with endothelial plasma membranes, thus bypassing intracellular organelles and minimizing lysosomal degradation. This suggests that the naturally formed ApoE corona in vivo may contribute to efficient cerebrovascular targeting, a property successfully replicated by the engineered ApoE corona strategy. In vivo biodistribution and kinetic studies demonstrated that especially ApoE-FL achieved enhanced brain-targeting efficiency, prolonged cerebrovascular retention, and extended targeting distance along the arteriovenous axis. This emphasizes that fusogenic liposomes effectively engage almost the entire microvascular network, including capillaries and post-capillary venules. Functionally, fusogenic liposome-delivered RSV improved blood-brain barrier (BBB) integrity, enhanced neurovascular coupling (NVC) responses, and promoted brain vascularization in aged mice. Single-cell RNA sequencing (scRNA-seq) revealed enhanced endothelial angiogenesis and barrier protective transcriptional profiles in cerebrovascular cells treated with ApoE-FL/RSV, suggesting a molecular basis for the observed vascular benefits. Liposomal RSV delivery achieved near-complete cerebrovascular and cognitive rejuvenation in aged mice applying a 2000-fold lower RSV dose than oral administration used as control sample. Thus, ApoE-FL liposomes exhibited exceptionally high delivery efficiency in deeper brain regions, further expanding their therapeutic potential. These findings underscore the importance of targeted drug delivery in optimizing therapeutic outcomes and establish ApoE-functionalized fusogenic liposomes as a promising strategy for mitigating brain vascular aging and cognitive decline. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/709925v1_ufig1.gif" ALT="Figure 1000"> View larger version (52K): org.highwire.dtl.DTLVardef@acad5borg.highwire.dtl.DTLVardef@a96e3borg.highwire.dtl.DTLVardef@18405aeorg.highwire.dtl.DTLVardef@90e349_HPS_FORMAT_FIGEXP M_FIG C_FIG

animal behavior and cognition↗

bioRxiv2026

Robust quality assessment of cryo-EM maps, tomograms and micrographs by statistics-based local resolution estimation

Resolution estimation by Fourier shell correlation (FSC) using half data sets is the standard method for map quality assessment in cryo-EM. Currently, the FSC method is largely used for refined cryo-EM maps in the context of single particle cryo-EM or subtomogram averaging. Here, we extended resolution estimation to assess the quality of electron micrographs, tilt-series and tomograms. We developed a robust statistics-based framework, capable of determining local quality estimates in the above cryo-EM data types. We show that the determined quality values on a micrograph and tomogram level can be used as a particle quality criterion to improve averaged 3D reconstructions. Using local quality assessments of tomograms, we were able to characterize tomogram quality dependence on distance inferred by radiation damage of FIB-milled lamella. This robust resolution-based quality assessment approach suitable for multiple cryo-EM data types opens new possibilities for automated quality control and method development in cryo-EM maps as well as tomograms and micrographs.

cell biology↗

bioRxiv2025

Membrane binding of a cyanobacterial ESCRT-III protein crucially involves the helix α1-3 hairpin conserved in all superfamily members

IM30, the inner membrane-associated protein of 30 kDa (also known as Vipp1) is essential for thylakoid membrane biogenesis and/or maintenance in chloroplasts and cyanobacteria. IM30 and its bacterial homolog PspA belong to the ESCRT-III superfamily, proteins previously thought to be restricted to eukaryotes and archaea. Despite low sequence similarity, IM30 shares key structural and functional features with eukaryotic ESCRT-IIIs, including a conserved 1-2 helical hairpin core and the ability to form oligomeric barrel- or rod assemblies that mediate membrane remodeling. Using IM30 variants, we now show that initial membrane recruitment of IM30 is driven by electrostatic interactions between the positively charged 1-3 helical hairpin and negatively charged lipid surfaces, paralleling the role of charged helical regions in some eukaryotic ESCRT-IIIs. This likely initiates lateral assembly of IM30 into higher-order barrel or rod structures on the membrane. Once assembled, 0 helices within these oligomers engage and stabilize internalized membrane tubules, mirroring membrane interaction strategies of eukaryotic ESCRT-IIIs, which use both N-terminal sequences and charged residues on 1/2. Thus, our findings demonstrate a conserved membrane binding and remodeling mechanism across the ESCRT-III superfamily, underscoring an evolutionary link in membrane dynamics between pro- and eukaryotes. SignificanceIM30, a membrane-associated protein found in cyanobacteria and chloroplasts, along with its bacterial homolog PspA, belongs to the ESCRT-III superfamily. Despite low sequence conservation, these proteins share structural and functional features with eukaryotic ESCRT-III proteins. We show that IM30 binds membranes via a conserved structural motif, followed by lateral assembly into higher-order complexes. This supports a mechanism of membrane remodeling that is conserved in prokaryotic and eukaryotic members of the ESCRT-III superfamily.

biochemistry↗

bioRxiv2025

The bacterial ESCRT-III PspA rods thin lipid tubules and and increase membrane curvature through helix α0 interactions

The phage shock protein A (PspA), a bacterial member of the ESCRT-III superfamily, forms rod-shaped helical assemblies that internalize membrane tubules. The N-terminal helix 0 of PspA (and other ESCRT-III members) has been suggested to act as a membrane anchor, the detailed mechanism, however, of how it binds to membranes and eventually triggers membrane fusion and/or fission events remains unclear. By solving a total of 15 cryo-electron microscopy (cryo-EM) structures of PspA and a truncation lacking the N-terminal helix 0 in the presence of EPL membranes, we show in molecular detail how PspA interacts with and remodels membranes: binding of the N-terminal helix 0 in the outer tubular membrane leaflet induces membrane curvature, supporting membrane tubulation by PspA. Detailed molecular dynamics simulations and free energy computations of interactions between the helix 0 and negatively charged membranes suggest a compensating mechanism between helix/membrane interactions and the energy contributions required for membrane bending. The energetic considerations are in line with the membrane structures observed in the cryo-EM images of tubulated membrane vesicles, fragmented vesicles inside tapered PspA rods, and shedded vesicles emerging at the thinner PspA rod ends. Our results provide insights into the molecular determinants and a potential mechanism of vesicular membrane remodeling mediated by a member of the ESCRT-III superfamily. SummaryThe rods of bacterial ESCRT-III protein PspA internalize and thin membrane tubules by overcoming the required bending energy through progressive membrane binding of the N-terminal helix in the PspA assembly.

biophysics↗

bioRxiv2025

CryoVIA - An image analysis toolkit for the quantification of membrane structures from cryo-EM micrographs

Imaging of lipid structures and associated protein complexes using electron cryo-microscopy (cryo-EM) is a common visualization and structure determination technique. The quantitative analysis of the membrane structures, however, is not routine and time consuming in particular when large amounts of data are involved. Here, we introduce the automated image-processing software cryo-vesicle image analyzer (CryoVIA) that parametrizes lipid structures of large data sets from cryo-EM images. This toolkit combines segmentation, structure identification with methods to automatically perform a large-scale data analysis of local and global membrane properties such as bilayer thickness, size, and curvature including membrane shape classifications. We included analyses of exemplary data sets of different lipid compositions and protein-induced lipid changes through an ESCRT-III membrane remodeling protein. The toolkit opens new possibilities to systematically study structural properties of membrane structures and their modifications from cryo-EM images.

bioinformatics↗

bioRxiv2024

Structural organization of p62 filaments and the cellular ultrastructure of calcium-rich p62-enwrapped lipid droplet cargo

The selective autophagy receptor p62/SQSTM1 (from hereon p62) is known to form higher-order filaments in vitro and to undergo liquid-liquid phase separation when mixed with poly-ubiquitin. We determined the full-length cryo-EM structure of p62 and elucidated a structured double helical filament scaffold composed of the PB1-domain associated with the flexible C-terminal part residing in the lumen and the solvent-accessible major groove. At different pH values and upon binding to soluble LC3, LC3-conjugated membranes and poly-ubiquitin, we observed p62 filament re-arrangements in the form of structural unwinding, disassembly, lateral association and bundling, respectively. In the cellular environment, under conditions of ATG5 knockdown leading to stalled autophagy, we imaged high-contrast layers consisting of p62 oligomers enwrapping lipid droplets by cryogenic electron tomography in cellulo, which we identified as calcium phosphate by compositional spectroscopy analysis. Together, we visualized the cellular ultrastructure of p62 oligomers with high calcium content as a potential intermediate step of autophagy initiation.

biophysics↗

bioRxiv2024

Structural basis for Vipp1 membrane binding: From loose coats and carpetsto ring and rod assemblies

Vipp1 (also known as IM30) is essential in most oxygenic photoautotrophic organisms. It is involved in membrane remodeling and fusion and is critical for thylakoid membrane biogenesis and maintenance. Vipp1 has recently been identified as a member of the ESCRT-III superfamily of membrane remodeling proteins, albeit it still is elusive how Vipp1 interacts with and finally remodels membranes. Here we present a series of cryo-EM structures of cyanobacterial Vipp1 interacting with bacterial membranes: first, we solved seven structures between 5 and 7 [A] resolution of three unique helical and four types of stacked-ring assemblies engulfing membranes, and, second, using sub-tomogram averaging, we determined three [~]20 [A] resolution structures compatible with previously observed carpet structures at three different membrane curvatures. By analyzing ten additional unique structures of N-terminally truncated Vipp1, we could show that helix 0 is essential for membrane tubulation and forms the membrane anchoring domain of Vipp1. Using a conformation-restrained Vipp1 mutant, we were able to reduce the structural plasticity of Vipp1 assemblies in the presence of lipids and determined two structures of Vipp1 at 3.0 [A] resolution, resolving the molecular details of membrane anchoring and intersubunit contacts of helix 0. Our data reveal the molecular details of how Vipp1 interacts with membranes, showing membrane curvature-dependent structural transitions from carpets to rings and rods, some of which are capable of inducing and/or stabilizing high local membrane curvature triggering membrane fusion. SummaryBacterial ESCRT-III family member Vipp1 forms membrane-bound coats, carpets, ring complexes, stacked-ring assemblies and helical tubes capable of internalizing lipids and inducing high membrane curvature.

biophysics↗

bioRxiv2024

Structural plasticity of bacterial ESCRT-III protein PspA in higher-orderassemblies

Eukaryotic members of the endosome sorting complex required for transport III (ESCRT-III) family have been shown to form diverse oligomeric assemblies. The bacterial phage shock protein A (PspA) has recently been identified as a bacterial member of the ESCRT-III superfamily, and monomeric PspA homo-oligomerizes to form large rod-shaped assemblies. As observed for eukaryotic ESCRT-III, PspA forms different tubular assemblies with varying diameters. Using electron cryo-microscopy (cryo-EM), we determined a total of 61 PspA structures and observed in molecular detail how structural plasticity of PspA rods is mediated by conformational changes at three hinge regions in the monomer and by the fixed as well as changing molecular contacts between protomers. Moreover, we reduced and increased the structural plasticity of PspA rods by removing the loop connecting helices 3/4 and the addition of nucleotides, respectively. Based on our analysis of PspA-mediated membrane remodeling, we suggest that the observed mode of structural plasticity is a prerequisite for the biological function of ESCRT-III superfamily members. SummaryA series of cryo-EM structures of PspA rods with induced diameter modulations reveals the molecular basis of structural plasticity.

biophysics↗

bioRxiv2024

Low-dose cryo-electron ptychography of proteins at sub-nanometer resolution

Cryo-transmission electron microscopy (cryo-EM) of frozen hydrated specimens is an efficient method for the structural analysis of purified biological molecules. However, cryo-EM and cryo-electron tomography are limited by the low signal-to-noise ratio (SNR) of recorded images, making detection of smaller particles challenging. For dose-resilient samples often studied in the physical sciences, electron ptychography - a coherent diffractive imaging technique using 4D scanning transmission electron microscopy (4D-STEM) - has recently demonstrated excellent SNR and resolution down to tens of picometers for thin specimens imaged at room temperature. Here we applied 4D-STEM and ptychographic data analysis to frozen hydrated proteins, reaching sub-nanometer resolution 3D reconstructions. We employed low-dose cryo-EM with an aberration-corrected, convergent electron beam to collect 4D-STEM data for our reconstructions. The high frame rate of the electron detector allowed us to record large datasets of electron diffraction patterns with substantial overlaps between the interaction volumes of adjacent scan positions, from which the scattering potentials of the samples were iteratively reconstructed. The reconstructed micrographs show strong SNR enabling the reconstruction of the structure of apoferritin protein at up to 5.8 [A] resolution. We also show structural analysis of the Phi92 capsid and sheath, tobacco mosaic virus, and bacteriorhodopsin at slightly lower resolutions.

biophysics↗

bioRxiv2023

Optical ice thickness measurement in the VitroJet for time-efficient single particle structure determination

Embedding biomolecules in vitreous ice of optimal thickness is critical for structure determination by cryo-electron microscopy. Ice thickness assessment and selection of suitable holes for data collection are currently part of time-consuming preparatory routines performed on expensive electron microscopes. To address this challenge, a routine has been developed to measure ice thickness during sample preparation using an optical camera integrated in the VitroJet. This method allows to estimate the ice thickness with an error below {+/-} 20 nm for ice layers in the range of 0 - 70 nm. Additionally, we implemented pin printing to reproduce and control sample deposition in the VitroJet. The median ice thickness can be reproduced with a standard deviation below {+/-} 11 nm for thicknesses up to 75 nm. Therefore, the ice thickness of buffer-suspended holes on an EM grid can be tuned and measured within the working range relevant for single particle cryo-EM. Single particle structures of apoferritin were determined at two distinct thicknesses of 30 nm and 70 nm. These reconstructions demonstrate the importance of ice thickness for time-efficient cryo-EM structure determination. HighlightsO_LIMethods in the VitroJet allow for on-the-fly ice thickness tuning and measurement C_LIO_LIThe optical camera can estimate ice thickness ranging from 0 - 70 {+/-} 20 nm C_LIO_LIPin printing enables to reproduce and control median ice thickness up to 75 {+/-} 11 nm C_LIO_LIStructures of apoferritin require 3.7 x fewer particles in 30 compared to 70 nm ice C_LI

molecular biology↗

bioRxiv2022

Extensive genomic divergence among 61 strains of Chlamydia psittaci

Chlamydia (C.) psittaci, the causative agent of avian chlamydiosis and human psittacosis, is a genetically heterogeneous species. Its broad host range includes parrots and many other birds, but occasionally also humans (via zoonotic transmission), ruminants, horses, swine and rodents. To assess whether there are genetic markers associated with host tropism we comparatively analyzed whole-genome sequences of 61 C. psittaci strains. Initially, poorly assembled genomes in public databases were subjected to clean-up, reassembly and polishing. Multiple sequence alignment of the genome sequences revealed four major clades within this species. Clade 1 represents the most recent lineage comprising 40/61 strains and contains 9/10 of the psittacine strains, including type strain 6BC, and 10/13 of human isolates. Clades 2-4 carry strains from different non-psittacine hosts. We found that clade membership correlates with classification schemes based on SNP types, ompA genotypes, multilocus sequence types as well as plasticity zone (PZ) structure and host preference. Genome analysis also revealed that i) sequence variation in the major outer membrane porin OmpA can result in 3D structural changes of immunogenic domains, ii) past host change of Clade 3 and 4 strains could be associated with loss of MAC/perforin in the PZ, rather than the large cytotoxin, iii) the distinct phylogeny of atypical strains (Clades 3 and 4) is also reflected in their repertoire of inclusion proteins (Inc family) and polymorphic membrane proteins (Pmps). Altogether, our study identified a number of genomic features that can be correlated with the phylogeny and host preference of C. psittaci strains.

genomics↗

bioRxiv2022

Structural plasticity of Atg18 oligomers: organization of assembled tubes and scaffolds at the isolation membrane

Autophagy-related protein 18 (Atg18) participates in the elongation of early autophagosomal structures in concert with Atg2 and Atg9 complexes. How Atg18 contributes to the structural coordination of Atg2 and Atg9 at the isolation membrane remains to be understood. Here, we determined the cryo-EM structures of Atg18 organized in helical tubes as well as soluble oligomers. The helical assembly is composed of Atg18 tetramers forming a lozenge cylindrical lattice with remarkable structural similarity to the COPII outer coat. When reconstituted with lipid membranes, using subtomogram averaging we determined tilted Atg18 dimer structures bridging two juxtaposed lipid membranes spaced apart by 80 [A]. Together with an AlphaFold Atg18-Atg2 model, we propose that Atg18 oligomers form a structural scaffold coordinating the Atg2 membrane bridge. The observed structural plasticity of Atg18s oligomeric organization and membrane binding provide a molecular framework for the positioning of downstream components of the autophagy machinery.

biophysics↗

bioRxiv2021

Single-particle cryo-EM structures from iDPC-STEM at near-atomic resolution

Electron cryo-microscopy (cryo-EM) is becoming one of the routine tools for structure determination of biological macromolecules. Commonly, molecular images are obtained by conventional transmission electron microcopy (CTEM) using underfocus and subsequently computationally combined into a high-resolution 3D structure. Here, we apply scanning transmission electron microscopy (STEM) using the integrated differential phase contrast mode also known as iDPC-STEM to the cryo-EM test specimen of tobacco mosaic virus (TMV). The micrographs show complete contrast transfer to high resolution and enable the cryo-EM structure determination at 3.5 [A] resolution using single-particle based helical reconstruction. A series of cryo-EM TMV maps was resolved at near-atomic resolution taken at different convergence semi-angle (CSA) beams and share identical features with maps obtained by CTEM of a previously acquired same-sized TMV data set. The associated map B-factors from iDPC-STEM match those obtained by CTEM recordings using 2nd generation direct electron detection devices. These data show that STEM imaging in general, and in particular the iDPC-STEM approach, can be applied to vitrified single-particle specimens to determine near-atomic resolution cryo-EM structures of biological macromolecules.

biophysics↗

bioRxiv2020

PspA maintains membrane integrity by an ESCRT-like membrane remodeling activity

PspA is the main effector of the phage shock protein (Psp) system and preserves the bacterial inner membrane integrity and function. Here, we present the 3.6 [A] resolution cryo-EM structure of PspA assembled in helical rods. PspA monomers adopt a canonical ESCRT-III fold in an extended open conformation. PspA rods are capable of enclosing lipids and generate positive membrane curvature. Using cryo-EM we visualized how PspA remodels membrane vesicles into m-sized structures and how it mediates the formation of internalized vesicular structures. Hot spots of these activities are zones derived from PspA assemblies, serving as lipid transfer platforms and linking previously separated lipid structures. These membrane fusion and fission activities are in line with the described functional properties of bacterial PspA/IM30/LiaH proteins. Our structural and functional analyses reveal that bacterial PspA belongs to the evolutionary ancestry of ESCRT-III proteins involved in membrane remodeling.

microbiology↗

bioRxiv2020

Adaptive FDR thresholding of Fourier shell correlation for resolution estimation of cryo-EM maps

Fourier shell correlation (FSC) has become a standard quantity for resolution estimation in electron cryo-microscopy. However, the resolution determination step is still subjective and not fully automated as it involves a series of map interventions before FSC computation and includes the selection of a common threshold. Here, we apply the statistical methods of permutation sampling and false discovery rate (FDR) control to the resolution-dependent correlation measure. The approach allows fully automated and mask-free resolution determination based on adaptive thresholding of FSC curves. We demonstrate the applicability for global, local and directional resolution estimation and show that the developed criterion termed FDR-FSC gives realistic resolution estimates based on a statistical significance criterion while eliminating the need of any map manipulations. The algorithms are implemented in a user-friendly GUI based software tool termed SPoC (https://github.com/MaximilianBeckers/SPOC).

biophysics↗

bioRxiv2019

Structural basis of p62/SQSTM1 helical filaments, their presence in p62 bodies and role in cargo recognition in the cell

p62/SQSTM1 is an autophagy receptor and signaling adaptor with an N-terminal PB1 domain that forms the scaffold of phase-separated p62 bodies in the cell. The molecular determinants that govern PB1 domain filament formation in vitro remain to be determined and the role of p62 filaments inside the cell is currently unclear. We determined four high-resolution cryo-EM structures of different human and Arabidopsis PB1 domain assemblies and observed a filamentous ultrastructure of phase-separated p62/SQSTM1 bodies using correlative cellular EM. We show that oligomerization or polymerization, driven by a double arginine finger in the PB1 domain, is a general requirement for lysosomal targeting of p62. Furthermore, the filamentous assembly state of p62 is required for autophagosomal processing of the p62-specific cargo KEAP1. Our results show that using such mechanisms, p62 filaments can be critical for cargo recognition and are an integral part of phase separated p62 bodies.

molecular biology↗

bioRxiv2019

Elucidation of the viral disassembly switch of tobacco mosaic virus

Stable capsid structures of viruses protect viral RNA while they also require controlled disassembly for releasing the viral genome in the host cell. A detailed understanding of viral disassembly processes and the involved structural switches is still lacking. Biochemically, this process has been extensively studied using the tobacco mosaic virus model system and carboxylate interactions have been proposed to play a critical part in this process. Here, we present two cryo-EM structures of the helical TMV assembly at 2.1 and 2.0 [A] resolution in conditions of high Ca2+ concentration at low pH and in water. Based on our atomic models, we identified the conformational details of the disassembly switch mechanism: in high Ca2+/acidic pH environment the virion is stabilized between neighboring subunits through carboxyl groups E95 and E97 in close proximity to a Ca2+ binding site. Upon increase in pH and lower Ca2+ levels, mutual repulsion of the E95/E97 pair and Ca2+ removal destabilize the network of interactions at lower radius and release the switch of virus disassembly. Our TMV structures revealed the conformational details for one of the reference systems of viral assembly/disassembly and provide the mechanistic explanation of a plethora of experimental results that were acquired over decades.\n\nSignificance StatementTobacco mosaic virus presents the text-book example of virus structure and RNA release from a viral capsid through disassembly. Despite the wealth of structural and biochemical data on the assembly/disassembly properties generated from more than 80 years of research, the atomic-resolution structural details of the proposed conformational changes have not been resolved to date. The here determined high-resolution cryo-EM structures reveal the conformational details of the molecular disassembly switch. When the virus enters the cell, carboxylate repulsion and loss of calcium-ion coordination destabilize the switch region and can trigger RNA release through virus disassembly. The two determined structural states resolve a long-standing question on environment-driven virus disassembly switches.

molecular biology↗