Insight into Cell-Entry Mechanisms of CPPs by Electron Microscopy

2010 ◽  
pp. 181-193 ◽  
Author(s):  
Kärt Padari ◽  
Annely Lorents ◽  
Eija Jokitalo ◽  
Margus Pooga
Keyword(s):  
Electron Microscopy ◽  
Cell Entry ◽  
Insight Into

The award of medals by the President, Sir Andrew Huxley, O.M., at the Anniversary Meeting, 30 November 1985

1986 ◽  
Vol 405 (1829) ◽  
pp. 181-184
Keyword(s):  
Electron Microscopy ◽  
Image Reconstruction ◽  
Coat Protein ◽  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Deep Insight ◽  
Living Matter ◽  
Fourier Image ◽  
Reconstruction Methods ◽  
Insight Into

The Copley Medal is awarded to Dr A. Klug, F. R. S., in recognition of his outstanding contributions to our understanding of complex biological structures and the methods used for determining them. Together with D. Kaspar, Klug developed a theory that predicted the arrangement of sub-units in the protein shells of spherical viruses. This theory brought order and understanding into a confused field ; nearly all the observed structures of small spherical viruses, many of them elucidated by Klug and his collaborators, are consistent with it. After more than 20 years’ work on tobacco mosaic virus Klug and his colleagues solved the structure of its coat protein in atomic detail. They also elucidated the mechanisms by which the helical virus particle assembles itself from its RNA and its 2130 protein sub-units. Recently his group succeeded in crystallizing chromatin, and solved its structure at a resolution sufficient to see the double-helical DNA coiled around the spool of histone. Many of Klug’s successes were made possible by his introduction of Fourier image reconstruction methods into electron microscopy. Klug’s work is characterized by deep insight into the physics of diffraction and image formation and the intricate geometry of living matter.

scholarly journals A Bacterial Microcompartment Is Used for Choline Fermentation byEscherichia coli536

2018 ◽  
Vol 200 (10) ◽  
Author(s):  
Taylor I. Herring ◽  
Tiffany N. Harris ◽  
Chiranjit Chowdhury ◽  
Sujit Kumar Mohanty ◽  
Thomas A. Bobik
Keyword(s):  
Electron Microscopy ◽  
Heart Disease ◽  
Gene Cluster ◽  
Transcriptional Regulator ◽  
Human Gut ◽  
Content Type ◽  
E Coli ◽  
Bacterial Microcompartment ◽  
New Type ◽  
Insight Into

ABSTRACTBacterial choline degradation in the human gut has been associated with cancer and heart disease. In addition, recent studies found that a bacterial microcompartment is involved in choline utilization byProteusandDesulfovibriospecies. However, many aspects of this process have not been fully defined. Here, we investigate choline degradation by the uropathogenEscherichia coli536. Growth studies indicatedE. coli536 degrades choline primarily by fermentation. Electron microscopy indicated that a bacterial microcompartment was used for this process. Bioinformatic analyses suggested that the choline utilization (cut) gene cluster ofE. coli536 includes two operons, one containing three genes and a main operon of 13 genes. Regulatory studies indicate that thecutXgene encodes a positive transcriptional regulator required for induction of the maincutoperon in response to choline supplementation. Each of the 16 genes in thecutcluster was individually deleted, and phenotypes were examined. ThecutX,cutY,cutF,cutO,cutC,cutD,cutU, andcutVgenes were required for choline degradation, but the remaining genes of thecutcluster were not essential under the conditions used. The reasons for these varied phenotypes are discussed.IMPORTANCEHere, we investigate choline degradation inE. coli536. These studies provide a basis for understanding a new type of bacterial microcompartment and may provide deeper insight into the link between choline degradation in the human gut and cancer and heart disease. These are also the first studies of choline degradation inE. coli536, an organism for which sophisticated genetic analysis methods are available. In addition, thecutgene cluster ofE. coli536 is located in pathogenicity island II (PAI-II536) and hence might contribute to pathogenesis.

Cryo-EM structure of the human cohesin-NIPBL-DNA complex

Science ◽  
2020 ◽  
Vol 368 (6498) ◽  
pp. 1454-1459 ◽  
Author(s):  
Zhubing Shi ◽  
Haishan Gao ◽  
Xiao-chen Bai ◽  
Hongtao Yu
Keyword(s):  
Electron Microscopy ◽  
Sister Chromatid ◽  
Base Pair ◽  
Adenosine Triphosphatase ◽  
Cryo Electron Microscopy ◽  
Synergistic Activation ◽  
Medium Resolution ◽  
Chromatid Cohesion ◽  
Dna Complex ◽  
Insight Into

As a ring-shaped adenosine triphosphatase (ATPase) machine, cohesin organizes the eukaryotic genome by extruding DNA loops and mediates sister chromatid cohesion by topologically entrapping DNA. How cohesin executes these fundamental DNA transactions is not understood. Using cryo–electron microscopy (cryo-EM), we determined the structure of human cohesin bound to its loader NIPBL and DNA at medium resolution. Cohesin and NIPBL interact extensively and together form a central tunnel to entrap a 72–base pair DNA. NIPBL and DNA promote the engagement of cohesin’s ATPase head domains and ATP binding. The hinge domains of cohesin adopt an “open washer” conformation and dock onto the STAG1 subunit. Our structure explains the synergistic activation of cohesin by NIPBL and DNA and provides insight into DNA entrapment by cohesin.

Binding of Tetrahymena dynein to axonemes of Marsilea vestita lacking the outer dynein arm

1985 ◽  
Vol 73 (1) ◽  
pp. 299-310
Author(s):  
J.S. Hyams
Keyword(s):  
Electron Microscopy ◽  
Polyacrylamide Gel Electrophoresis ◽  
Valuable Insight ◽  
Marsilea Vestita ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
And Function ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Axonemes from the heterosporous water fern Marsilea vestita were fixed in the presence of tannic acid and examined by thin-section electron microscopy. Transverse sections revealed the normal 9+2 configuration except for the absence of the outer of the two dynein arms. Both arms were normally preserved in parallel preparations of Chlamydomonas axonemes. Isolated dynein from the ciliated protozoon Tetrahymena bound to Marsilea axonemes at the site normally occupied by the outer arm. Dynein binding was partially reversed by ATP as judged by both electron microscopy and polyacrylamide gel electrophoresis. This system should provide a valuable insight into the biochemistry and function of the inner dynein arm and the relationship of the two arms to motility in more conventionally equipped axonemes.

Characterization of Electrophoretic Lipoprotein Fractions: Immunochemical and Electron Microscopic Studies

1972 ◽  
Vol 18 (6) ◽  
pp. 534-538
Author(s):  
Mario Werner ◽  
Albert L Jones
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Electrophoretic Pattern ◽  
Electron Microscopic ◽  
Lipoprotein Subfractions ◽  
New Techniques ◽  
Microscopic Studies ◽  
Insight Into

Abstract To improve the characterization of electrophoretic lipoprotein subfractions, we developed two new techniques for analyzing lipoproteins after electrophoresis on thin agarose layers. Overlay with antisera exactly localizes specific apoproteins without any distortion caused by antigen diffusion; electron microscopy of eluted fractions determines the varying particle-size distribution. Applied together, these methods can detect individual differences between hyperlipemic samples that are not immediately apparent in the electrophoretic pattern, and should provide valuable new insight into the classification of hyperlipoproteinemias.

scholarly journals SARS-CoV-2 and Three Related Coronaviruses Utilize Multiple ACE2 Orthologs and Are Potently Blocked by an Improved ACE2-Ig

2020 ◽  
Vol 94 (22) ◽  
Author(s):  
Yujun Li ◽  
Haimin Wang ◽  
Xiaojuan Tang ◽  
Shisong Fang ◽  
Danting Ma ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Viral Infections ◽  
Cell Entry ◽  
Etiological Agent ◽  
Wild Mammals ◽  
Domestic Species ◽  
Support Cell ◽  
Wide Range ◽  
The Future ◽  
Insight Into

ABSTRACT The ongoing coronavirus disease 2019 (COVID-19) pandemic has caused >20 million infections and >750,000 deaths. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, has been found closely related to the bat coronavirus strain RaTG13 (Bat-CoV RaTG13) and a recently identified pangolin coronavirus (Pangolin-CoV-2020). Here, we first investigated the ability of SARS-CoV-2 and three related coronaviruses to utilize animal orthologs of angiotensin-converting enzyme 2 (ACE2) for cell entry. We found that ACE2 orthologs of a wide range of domestic and wild mammals, including camels, cattle, horses, goats, sheep, cats, rabbits, and pangolins, were able to support cell entry of SARS-CoV-2, suggesting that these species might be able to harbor and spread this virus. In addition, the pangolin and bat coronaviruses, Pangolin-CoV-2020 and Bat-CoV RaTG13, were also found able to utilize human ACE2 and a number of animal-ACE2 orthologs for cell entry, indicating risks of spillover of these viruses into humans in the future. We then developed potently anticoronavirus ACE2-Ig proteins that are broadly effective against the four distinct coronaviruses. In particular, through truncating ACE2 at its residue 740 but not 615, introducing a D30E mutation, and adopting an antibody-like tetrameric-ACE2 configuration, we generated an ACE2-Ig variant that neutralizes SARS-CoV-2 at picomolar range. These data demonstrate that the improved ACE2-Ig variants developed in this study could potentially be developed to protect from SARS-CoV-2 and some other SARS-like viruses that might spillover into humans in the future. IMPORTANCE The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent of the currently uncontrolled coronavirus disease 2019 (COVID-19) pandemic. It is important to study the host range of SARS-CoV-2, because some domestic species might harbor the virus and transmit it back to humans. In addition, insight into the ability of SARS-CoV-2 and SARS-like viruses to utilize animal orthologs of the SARS-CoV-2 receptor ACE2 might provide structural insight into improving ACE2-based viral entry inhibitors. In this study, we found that ACE2 orthologs of a wide range of domestic and wild animals can support cell entry of SARS-CoV-2 and three related coronaviruses, providing insights into identifying animal hosts of these viruses. We also developed recombinant ACE2-Ig proteins that are able to potently block these viral infections, providing a promising approach to developing antiviral proteins broadly effective against these distinct coronaviruses.

scholarly journals Opsonization Modulates Rac-1 Activation during Cell Entry by Leishmania amazonensis

2002 ◽  
Vol 70 (8) ◽  
pp. 4571-4580 ◽  
Author(s):  
J. Morehead ◽  
I. Coppens ◽  
N. W. Andrews
Keyword(s):  
Cho Cells ◽  
Chinese Hamster ◽  
Cytochalasin D ◽  
Leishmania Amazonensis ◽  
Cell Entry ◽  
Butanedione Monoxime ◽  
Respiratory Burst Oxidase ◽  
Insight Into ◽  
Host Tissues

ABSTRACT Lesions caused by Leishmania amazonensis normally heal, but relapses occur due to parasite persistence in host tissues. It has been proposed that infection of fibroblasts plays an important role in this process by providing the parasites with a safe haven in which to replicate. However, most previous studies have focused on the entry of Leishmania into macrophages, a process mediated by serum opsonins. To gain insight into a possible role of nonopsonic entry in the intracellular persistence of amastigotes, we examined the invasion of Chinese hamster ovary (CHO) cells. Amastigotes entered CHO cells by a cytochalasin D, genistein, wortmannin, and 2,3-butanedione monoxime-sensitive pathway and replicated within phagolysosomes. However, unlike most phagocytic processes described to date, amastigote internalization in CHO cells involved activation of the GTPases Rho and Cdc42 but not Rac-1. When uptake was mediated by fibronectin or when amastigotes were opsonized with immunoglobulin G and internalized by Fc receptor-expressing CHO cells, Rac-1 activation was restored and found to be required for parasite internalization. Given the essential role of Rac in assembly of the respiratory burst oxidase, invasion through this nonopsonic, Rac-1-independent pathway may play a central role in the intracellular survival of Leishmania in immune hosts.

Sign in / Sign up

Export Citation Format

Share Document