Search results for "Cryoelectron microscopy"

Cryo-EM structure of ssDNA bacteriophage ΦCjT23 provides insight into early virus evolution.

2022

AbstractThe origin of viruses remains an open question. While lack of detectable sequence similarity hampers the analysis of distantly related viruses, structural biology investigations of conserved capsid protein structures facilitate the study of distant evolutionary relationships. Here we characterize the lipid-containing ssDNA temperate bacteriophage ΦCjT23, which infects Flavobacterium sp. (Bacteroidetes). We report ΦCjT23-like sequences in the genome of strains belonging to several Flavobacterium species. The virion structure determined by cryogenic electron microscopy reveals similarities to members of the viral kingdom Bamfordvirae that currently consists solely of dsDNA viruses wit…

Virus found in a boreal lake links ssDNA and dsDNA viruses.

2017

Viruses have impacted the biosphere in numerous ways since the dawn of life. However, the evolution, genetic, structural, and taxonomic diversity of viruses remain poorly understood, in part because sparse sampling of the virosphere has concentrated mostly on exploring the abundance and diversity of dsDNA viruses. Furthermore, viral genomes are highly diverse, and using only the current sequence-based methods for classifying viruses and studying their phylogeny is complicated. Here we describe a virus, FLiP (Flavobacterium-infecting, lipid-containing phage), with a circular ssDNA genome and an internal lipid membrane enclosed in the icosahedral capsid. The 9,174-nt-long genome showed limite…

Where do we go from here? Membrane protein research beyond the structure-function horizon.

2018

Encapsulation mechanisms and structural studies of GRM2 bacterial microcompartment particles

2019

Bacterial microcompartments (BMCs) are prokaryotic organelles consisting of a protein shell and an encapsulated enzymatic core. BMCs are involved in several biochemical processes, such as choline, glycerol and ethanolamine degradation and carbon fixation. Since non-native enzymes can also be encapsulated in BMCs, an improved understanding of BMC shell assembly and encapsulation processes could be useful for synthetic biology applications. Here we report the isolation and recombinant expression of BMC structural genes from the Klebsiella pneumoniae GRM2 locus, the investigation of mechanisms behind encapsulation of the core enzymes, and the characterization of shell particles by cryo-EM. We …

Structure of AP205 Coat Protein Reveals Circular Permutation in ssRNA Bacteriophages.

2016

We are thankful to the MAX-lab staff for their support during our visit at the synchrotron.; International audience; AP205 is a single-stranded RNA bacteriophage that has a coat protein sequence not similar to any other known single-stranded RNA phage. Here, we report an atomic-resolution model of the AP205 virus-like particle based on a crystal structure of an unassembled coat protein dimer and a cryo-electron microscopy reconstruction of the assembled particle, together with secondary structure information from site-specific solid-state NMR data. The AP205 coat protein dimer adopts the conserved Leviviridae coat protein fold except for the N-terminal region, which forms a beta-hairpin in …

Exploiting Cryo-EM Structural Information and All-Atom Simulations To Decrypt the Molecular Mechanism of Splicing Modulators.

2019

Splicing modulators (SMs) pladienolides, herboxidienes, and spliceostatins exert their antitumor activity by altering the ability of SF3B1 and PHF5A proteins, components of SF3b splicing factor, to recognize distinct intron branching point sequences, thus finely calibrating constitutive/alternative/aberrant splicing of pre-mRNA. Here, by exploiting structural information obtained from cryo-EM data, and by performing multiple μs-long all-atom simulations of SF3b in apo form and in complex with selected SMs, we disclose how these latter seep into the narrow slit at the SF3B1/PHF5A protein interface. This locks the intrinsic open/closed conformational transitions of SFB1's solenoidal structure…

3-D reconstruction of hemocyanins and other invertebrate hemolymph proteins by cryo-TEM: an overview.

2004

Structure of the Cryptosporidium parvum microneme: a metabolically and osmotically labile apicomplexan organelle.

2003

From an EM study of thin sections, the rod-like microneme organelles within conventionally glutaraldehyde fixed Cryptosporidium parvum sporozoites have been shown to undergo a shape change to a more spherical structure when the sporozoites age in vitro for a period of approximately 12 to 24 h. This correlates with the shape change of intact sporozoites, from motile hence viable thin banana-shaped cells to swollen pear-shaped cells, shown by differential interference contrast light microscopy of unstained unfixed and glutaraldehyde-fixed samples, as well as by thin section EM of fixed sporozoites. From negatively stained EM specimens of unfixed and fixed sporozoites the cellular shape change…

Crystal Structure of the Maturation Protein from Bacteriophage Qβ

2017

Abstract Virions of the single-stranded RNA bacteriophages contain a single copy of the maturation protein, which is bound to the phage genome and is required for the infectivity of the particles. The maturation protein mediates the adsorption of the virion to bacterial pili and the subsequent release and penetration of the genome into the host cell. Here, we report a crystal structure of the maturation protein from bacteriophage Qβ. The protein has a bent, highly asymmetric shape and spans 110 A in length. Apart from small local substructures, the overall fold of the maturation protein does not resemble that of other known proteins. The protein is organized in two distinct regions, an α-he…

Amylopectin: a major component of the residual body inCryptosporidium parvumoocysts

2004

Amylopectin is used for carbohydrate storage in different life-stages of a number of apicomplexan parasites. We have performed an ultrastructural analysis of amylopectin granules from the oocyst residual body and sporozoites ofCryptosporidium parvum. Amylopectin granules were studiedin situand after isolation from ‘French’ press disrupted parasites, by conventional transmission electron microscopy (TEM) of sectioned oocysts and various negative staining and cryoelectron microscopy techniques. Within the membrane-enclosed oocyst residuum large amylopectin granules (0·1–0·3 μm) can be found besides a characteristic large lipid body and a crystalline protein inclusion. Smaller granules were de…