scholarly journals Structure of the Ty3/Gypsy retrotransposon capsid and the evolution of retroviruses

2019 ◽  
Vol 116 (20) ◽  
pp. 10048-10057 ◽  
Author(s):  
Svetlana O. Dodonova ◽  
Simone Prinz ◽  
Virginia Bilanchone ◽  
Suzanne Sandmeyer ◽  
John A. G. Briggs
Keyword(s):  
Electron Tomography ◽  
Structural Data ◽  
Endogenous Retroviruses ◽  
Structural Basis ◽  
Ltr Retrotransposons ◽  
Placental Development ◽  
Infectious Particle ◽  
Cryo Electron Microscopy ◽  
Virus Like Particle ◽  
Gypsy Retrotransposon

Retroviruses evolved from long terminal repeat (LTR) retrotransposons by acquisition of envelope functions, and subsequently reinvaded host genomes. Together, endogenous retroviruses and LTR retrotransposons represent major components of animal, plant, and fungal genomes. Sequences from these elements have been exapted to perform essential host functions, including placental development, synaptic communication, and transcriptional regulation. They encode a Gag polypeptide, the capsid domains of which can oligomerize to form a virus-like particle. The structures of retroviral capsids have been extensively described. They assemble an immature viral particle through oligomerization of full-length Gag. Proteolytic cleavage of Gag results in a mature, infectious particle. In contrast, the absence of structural data on LTR retrotransposon capsids hinders our understanding of their function and evolutionary relationships. Here, we report the capsid morphology and structure of the archetypal Gypsy retrotransposon Ty3. We performed electron tomography (ET) of immature and mature Ty3 particles within cells. We found that, in contrast to retroviruses, these do not change size or shape upon maturation. Cryo-ET and cryo-electron microscopy of purified, immature Ty3 particles revealed an irregular fullerene geometry previously described for mature retrovirus core particles and a tertiary and quaternary arrangement of the capsid (CA) C-terminal domain within the assembled capsid that is conserved with mature HIV-1. These findings provide a structural basis for studying retrotransposon capsids, including those domesticated in higher organisms. They suggest that assembly via a structurally distinct immature capsid is a later retroviral adaptation, while the structure of mature assembled capsids is conserved between LTR retrotransposons and retroviruses.

Cryo Electron Microscopy of SSV1 phage particles

1995 ◽  
Vol 53 ◽  
pp. 842-843
Author(s):  
U. Ziese ◽  
D. Typke ◽  
R. Hegerl ◽  
W. Baumeister
Keyword(s):  
Electron Microscopy ◽  
Periodic Structure ◽  
Low Dose ◽  
Electron Tomography ◽  
Structural Data ◽  
Mass Determination ◽  
The Third ◽  
Negative Stain ◽  
Cryo Electron Microscopy ◽  
Thermophilic Archaeon

SSVl phages are lemon-shaped particles, normally about 90 nm x 40 nm in size, with short tail fibres attached to one pole, produced by the thermophilic archaeon Sulfolobus shibate, isolate B12. They are made of 3 different proteins and DNA (15.5 kbp). Two proteins, together with host lipid, form the envelope, the third protein is associated with the DNA. Interestingly, this virus produces particles of varying size and shape. We have investigated the mass of the virions by STEM mass determination, the inner structure by cryo-electron microscopy, and the shape variability by electron tomography. Automatic electron tomography (AET) has been shown to be a useful technique for collecting 3D structural data of individual biological particles under low dose conditions, in negative stain as well as in frozen-hydrated preparations.Taking electron micrographs of vitrified samples we obtained images revealing some details of the inner structure and, on some particles, a periodic structure of the envelope. (Fig. 1a-b) The inner structure has periodicities of about 2.5 nm, which is in agreement with that found by Lepault et al on vitrified samples of the phages lambda and T4.

scholarly journals Structural basis of GIRK2 channel modulation by cholesterol and PIP2

2020 ◽  
Author(s):  
Yamuna Kalyani Mathiharan ◽  
Ian W. Glaaser ◽  
Yulin Zhao ◽  
Michael J. Robertson ◽  
Georgios Skiniotis ◽  
...  
Keyword(s):  
G Protein ◽  
Transmembrane Domain ◽  
Structural Data ◽  
Structural Basis ◽  
Girk Channels ◽  
Channel Modulation ◽  
Cryo Electron Microscopy ◽  
Cellular Excitability ◽  
Cholesteryl Hemisuccinate ◽  
Inwardly Rectifying

ABSTRACTG protein-gated inwardly rectifying potassium (GIRK) channels play important roles in controlling cellular excitability in the heart and brain. While structural data begin to unravel the molecular basis for G protein and alcohol dependent activation of GIRK channels, little is known about the modulation by cholesterol. Here, we present cryo-electron microscopy (cryoEM) structures of GIRK2 in the presence and absence of the cholesterol analog cholesteryl hemisuccinate (CHS), and PIP2. The structures and their comparison reveal that CHS binds near PIP2 in lipid-facing hydrophobic pockets of the transmembrane domain (TMD). CHS potentiates the effects of PIP2, which stabilizes the inter-domain region and promotes the engagement of the cytoplasmic domain (CTD) onto the transmembrane region. The results suggest that CHS acts as a positive allosteric modulator and identify novel therapeutic sites for modulating GIRK channels in the brain.

scholarly journals Tubulin glycylation controls axonemal dynein activity, flagellar beat, and male fertility

Science ◽  
2021 ◽  
Vol 371 (6525) ◽  
pp. eabd4914
Author(s):  
Sudarshan Gadadhar ◽  
Gonzalo Alvarez Viar ◽  
Jan Niklas Hansen ◽  
An Gong ◽  
Aleksandr Kostarev ◽  
...  
Keyword(s):  
Posttranslational Modifications ◽  
Male Fertility ◽  
Electron Tomography ◽  
Structural Basis ◽  
Cellular Functions ◽  
Flagellar Beat ◽  
Cryo Electron Tomography ◽  
Axonemal Dynein ◽  
Dynein Arms ◽  
Cilia And Flagella

Posttranslational modifications of the microtubule cytoskeleton have emerged as key regulators of cellular functions, and their perturbations have been linked to a growing number of human pathologies. Tubulin glycylation modifies microtubules specifically in cilia and flagella, but its functional and mechanistic roles remain unclear. In this study, we generated a mouse model entirely lacking tubulin glycylation. Male mice were subfertile owing to aberrant beat patterns of their sperm flagella, which impeded the straight swimming of sperm cells. Using cryo–electron tomography, we showed that lack of glycylation caused abnormal conformations of the dynein arms within sperm axonemes, providing the structural basis for the observed dysfunction. Our findings reveal the importance of microtubule glycylation for controlled flagellar beating, directional sperm swimming, and male fertility.

scholarly journals Structural basis for the regulation of nucleosome recognition and HDAC activity by histone deacetylase assemblies

2021 ◽  
Vol 7 (2) ◽  
pp. eabd4413
Author(s):  
Jung-Hoon Lee ◽  
Daniel Bollschweiler ◽  
Tillman Schäfer ◽  
Robert Huber
Keyword(s):  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Active Sites ◽  
Chromatin Modification ◽  
Structural Basis ◽  
Amino Terminal ◽  
Cryo Electron Microscopy ◽  
Multiple Contacts ◽  
Lysine Residues ◽  
Nucleosome Binding

The chromatin-modifying histone deacetylases (HDACs) remove acetyl groups from acetyl-lysine residues in histone amino-terminal tails, thereby mediating transcriptional repression. Structural makeup and mechanisms by which multisubunit HDAC complexes recognize nucleosomes remain elusive. Our cryo–electron microscopy structures of the yeast class II HDAC ensembles show that the HDAC protomer comprises a triangle-shaped assembly of stoichiometry Hda12-Hda2-Hda3, in which the active sites of the Hda1 dimer are freely accessible. We also observe a tetramer of protomers, where the nucleosome binding modules are inaccessible. Structural analysis of the nucleosome-bound complexes indicates how positioning of Hda1 adjacent to histone H2B affords HDAC catalysis. Moreover, it reveals how an intricate network of multiple contacts between a dimer of protomers and the nucleosome creates a platform for expansion of the HDAC activities. Our study provides comprehensive insight into the structural plasticity of the HDAC complex and its functional mechanism of chromatin modification.

scholarly journals Capturing Enveloped Viruses on Affinity Grids for Downstream Cryo-Electron Microscopy Applications

2013 ◽  
Vol 20 (1) ◽  
pp. 164-174 ◽  
Author(s):  
Gabriella Kiss ◽  
Xuemin Chen ◽  
Melinda A. Brindley ◽  
Patricia Campbell ◽  
Claudio L. Afonso ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Measles Virus ◽  
Influenza A ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Nitrilotriacetic Acid ◽  
Dimensional Structure ◽  
Enveloped Viruses ◽  
Cryo Electron Microscopy ◽  
Human Immunodeficiency Virus Virus

AbstractElectron microscopy (EM), cryo-electron microscopy (cryo-EM), and cryo-electron tomography (cryo-ET) are essential techniques used for characterizing basic virus morphology and determining the three-dimensional structure of viruses. Enveloped viruses, which contain an outer lipoprotein coat, constitute the largest group of pathogenic viruses to humans. The purification of enveloped viruses from cell culture presents certain challenges. Specifically, the inclusion of host-membrane-derived vesicles, the complete destruction of the viruses, and the disruption of the internal architecture of individual virus particles. Here, we present a strategy for capturing enveloped viruses on affinity grids (AG) for use in both conventional EM and cryo-EM/ET applications. We examined the utility of AG for the selective capture of human immunodeficiency virus virus-like particles, influenza A, and measles virus. We applied nickel-nitrilotriacetic acid lipid layers in combination with molecular adaptors to selectively adhere the viruses to the AG surface. This further development of the AG method may prove essential for the gentle and selective purification of enveloped viruses directly onto EM grids for ultrastructural analyses.

scholarly journals Endogenous Retroviruses in Trophoblast Differentiation and Placental Development

2010 ◽  
Vol 64 (4) ◽  
pp. 255-264 ◽  
Author(s):  
Sarah G. Black ◽  
Fredrick Arnaud ◽  
Massimo Palmarini ◽  
Thomas E. Spencer
Keyword(s):  
Endogenous Retroviruses ◽  
Placental Development ◽  
Trophoblast Differentiation

scholarly journals Structural insights into the conformational plasticity of the full-length trimeric HIV-1 envelope glycoprotein precursor

2018 ◽  
Author(s):  
Shijian Zhang ◽  
Wei Li Wang ◽  
Shuobing Chen ◽  
Maolin Lu ◽  
Eden P. Go ◽  
...  
Keyword(s):  
Viral Entry ◽  
Envelope Glycoprotein ◽  
Structural Data ◽  
Full Length ◽  
Heptad Repeat ◽  
Structural Basis ◽  
Glycoprotein Precursor ◽  
Helix Bundle ◽  
Conformational Plasticity ◽  
Hiv 1

SummaryThe human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer mediates viral entry into cells and is the major target for the host antibody response. In infected cells, the mature Env [(gp120/gp41)3] is produced by cleavage of a trimeric gp160 precursor. Proteolytic cleavage decreases Env conformational flexibility, allowing the mature Env to resist antibody binding to conserved elements. The conformational plasticity of the Env precursor skews the humoral immune response towards the elicitation of ineffectual antibodies, contributing to HIV-1 persistence in the infected host. The structural basis for the plasticity of the Env precursor remains elusive. Here we use cryo-electron microscopy to visualize two coexisting conformational states of the full-length Env precursor at nominal resolutions of 5.5 and 8.0 Å. The State-P2 conformation features a three-helix bundle of the gp41 heptad repeat region in the core, but has disordered membrane-interactive regions. State-P1 trimers lack the three-helix bundle and instead retain ordered transmembrane and membrane-proximal external regions embracing a central cavity. Our structural data shed light on the unusual plasticity of the Env precursor and provide new clues to Env immunogen discovery.

scholarly journals Structural insights into the activation of human calcium-sensing receptor

2021 ◽  
Author(s):  
Xiaochen Chen ◽  
Lu Wang ◽  
Zhanyu Ding ◽  
Qianqian Cui ◽  
Li Han ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Large Scale ◽  
Transmembrane Domains ◽  
Structural Basis ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Cryo Electron Microscopy ◽  
Activation Mechanisms ◽  
G Protein Coupled ◽  
Structural Insights

AbstractHuman calcium-sensing receptor (CaSR) is a G-protein-coupled receptor that maintains Ca2+ homeostasis in serum. Here, we present the cryo-electron microscopy structures of the CaSR in the inactive and active states. Complemented with previously reported crystal structures of CaSR extracellular domains, it suggests that there are three distinct conformations: inactive, intermediate and active state during the activation. We used a negative allosteric nanobody to stabilize the CaSR in the fully inactive state and found a new binding site for Ca2+ ion that acts as a composite agonist with L-amino acid to stabilize the closure of active Venus flytraps. Our data shows that the agonist binding leads to the compaction of the dimer, the proximity of the cysteine-rich domains, the large-scale transitions of 7-transmembrane domains, and the inter-and intrasubunit conformational changes of 7-transmembrane domains to accommodate the downstream transducers. Our results reveal the structural basis for activation mechanisms of the CaSR.

scholarly journals Cryo-EM structure of human mitochondrial trifunctional protein

2018 ◽  
Vol 115 (27) ◽  
pp. 7039-7044 ◽  
Author(s):  
Kai Liang ◽  
Ningning Li ◽  
Xiao Wang ◽  
Jianye Dai ◽  
Pulan Liu ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Oxidation Process ◽  
Structural Basis ◽  
Acid Oxidation ◽  
Cryo Electron Microscopy ◽  
Helical Hairpin ◽  
Tetrameric Structure ◽  
Acute Fatty Liver ◽  
Mitochondrial Trifunctional Protein

The mitochondrial trifunctional protein (TFP) catalyzes three reactions in the fatty acid β-oxidation process. Mutations in the two TFP subunits cause mitochondrial trifunctional protein deficiency and acute fatty liver of pregnancy that can lead to death. Here we report a 4.2-Å cryo-electron microscopy α2β2 tetrameric structure of the human TFP. The tetramer has a V-shaped architecture that displays a distinct assembly compared with the bacterial TFPs. A concave surface of the TFP tetramer interacts with the detergent molecules in the structure, suggesting that this region is involved in associating with the membrane. Deletion of a helical hairpin in TFPβ decreases its binding to the liposomes in vitro and reduces its membrane targeting in cells. Our results provide the structural basis for TFP function and have important implications for fatty acid oxidation related diseases.

scholarly journals Direct binding of TFEα opens DNA binding cleft of RNA polymerase

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Sung-Hoon Jun ◽  
Jaekyung Hyun ◽  
Jeong Seok Cha ◽  
Hoyoung Kim ◽  
Michael S. Bartlett ◽  
...  
Keyword(s):  
Dna Binding ◽  
Rna Polymerase ◽  
Transcription Initiation ◽  
Structural Basis ◽  
Transcription Bubble ◽  
Cryo Electron Microscopy ◽  
Direct Binding ◽  
Binding Cleft ◽  
Promoter Dna ◽  
Winged Helix Domain

AbstractOpening of the DNA binding cleft of cellular RNA polymerase (RNAP) is necessary for transcription initiation but the underlying molecular mechanism is not known. Here, we report on the cryo-electron microscopy structures of the RNAP, RNAP-TFEα binary, and RNAP-TFEα-promoter DNA ternary complexes from archaea, Thermococcus kodakarensis (Tko). The structures reveal that TFEα bridges the RNAP clamp and stalk domains to open the DNA binding cleft. Positioning of promoter DNA into the cleft closes it while maintaining the TFEα interactions with the RNAP mobile modules. The structures and photo-crosslinking results also suggest that the conserved aromatic residue in the extended winged-helix domain of TFEα interacts with promoter DNA to stabilize the transcription bubble. This study provides a structural basis for the functions of TFEα and elucidates the mechanism by which the DNA binding cleft is opened during transcription initiation in the stalk-containing RNAPs, including archaeal and eukaryotic RNAPs.

Sign in / Sign up

Export Citation Format

Share Document