scholarly journals Plant-expressed virus-like particles reveal the intricate maturation process of a eukaryotic virus

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Roger Castells-Graells ◽  
Jonas R. S. Ribeiro ◽  
Tatiana Domitrovic ◽  
Emma L. Hesketh ◽  
Charlotte A. Scarff ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Large Scale ◽  
Biologically Active ◽  
Host Cells ◽  
Maturation Process ◽  
Virus Maturation ◽  
Autocatalytic Cleavage ◽  
Virus Capsids ◽  
Rigid Body Motions ◽  
Expression Time

AbstractMany virus capsids undergo exquisitely choreographed maturation processes in their host cells to produce infectious virions, and these remain poorly understood. As a tool for studying virus maturation, we transiently expressed the capsid protein of the insect virus Nudaurelia capensis omega virus (NωV) in Nicotiana benthamiana and were able to purify both immature procapsids and mature capsids from infiltrated leaves by varying the expression time. Cryo-EM analysis of the plant-produced procapsids and mature capsids to 6.6 Å and 2.7 Å resolution, respectively, reveals that in addition to large scale rigid body motions, internal regions of the subunits are extensively remodelled during maturation, creating the active site required for autocatalytic cleavage and infectivity. The mature particles are biologically active in terms of their ability to lyse membranes and have a structure that is essentially identical to authentic virus. The ability to faithfully recapitulate and visualize a complex maturation process in plants, including the autocatalytic cleavage of the capsid protein, has revealed a ~30 Å translation-rotation of the subunits during maturation as well as conformational rearrangements in the N and C-terminal helical regions of each subunit.

scholarly journals The Mysterious Unfoldome: Structureless, Underappreciated, Yet Vital Part of Any Given Proteome

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Vladimir N. Uversky
Keyword(s):  
Large Scale ◽  
Intrinsically Disordered Proteins ◽  
Biologically Active ◽  
Disordered Proteins ◽  
Unfolded Proteins ◽  
Intrinsically Disordered ◽  
Proteome Level ◽  
Natively Unfolded ◽  
Natively Unfolded Proteins

Contrarily to the general believe, many biologically active proteins lack stable tertiary and/or secondary structure under physiological conditions in vitro. These intrinsically disordered proteins (IDPs) are highly abundant in nature and many of them are associated with various human diseases. The functional repertoire of IDPs complements the functions of ordered proteins. Since IDPs constitute a significant portion of any given proteome, they can be combined in an unfoldome; which is a portion of the proteome including all IDPs (also known as natively unfolded proteins, therefore, unfoldome), and describing their functions, structures, interactions, evolution, and so forth. Amino acid sequence and compositions of IDPs are very different from those of ordered proteins, making possible reliable identification of IDPs at the proteome level by various computational means. Furthermore, IDPs possess a number of unique structural properties and are characterized by a peculiar conformational behavior, including their high stability against low pH and high temperature and their structural indifference toward the unfolding by strong denaturants. These peculiarities were shown to be useful for elaboration of the experimental techniques for the large-scale identification of IDPs in various organisms. Some of the computational and experimental tools for the unfoldome discovery are discussed in this review.

scholarly journals Atomistic simulations indicate the functional loop-to-coiled-coil transition in influenza hemagglutinin is not downhill

2018 ◽  
Vol 115 (34) ◽  
pp. E7905-E7913 ◽  
Author(s):  
Xingcheng Lin ◽  
Jeffrey K. Noel ◽  
Qinghua Wang ◽  
Jianpeng Ma ◽  
José N. Onuchic
Keyword(s):  
Viral Entry ◽  
Large Scale ◽  
Coiled Coil ◽  
Structural Rearrangement ◽  
Structural Heterogeneity ◽  
Host Cells ◽  
Fusion Peptides ◽  
Influenza Hemagglutinin ◽  
Loop Region ◽  
Coil Transition

Influenza hemagglutinin (HA) mediates viral entry into host cells through a large-scale conformational rearrangement at low pH that leads to fusion of the viral and endosomal membranes. Crystallographic and biochemical data suggest that a loop-to-coiled-coil transition of the B-loop region of HA is important for driving this structural rearrangement. However, the microscopic picture for this proposed “spring-loaded” movement is missing. In this study, we focus on understanding the transition of the B loop and perform a set of all-atom molecular dynamics simulations of the full B-loop trimeric structure with the CHARMM36 force field. The free-energy profile constructed from our simulations describes a B loop that stably folds half of the postfusion coiled coil in tens of microseconds, but the full coiled coil is unfavorable. A buried hydrophilic residue, Thr59, is implicated in destabilizing the coiled coil. Interestingly, this conserved threonine is the only residue in the B loop that strictly differentiates between the group 1 and 2 HA molecules. Microsecond-scale constant temperature simulations revealed that kinetic traps in the structural switch of the B loop can be caused by nonnative, intramonomer, or intermonomer β-sheets. The addition of the A helix stabilized the postfusion state of the B loop, but introduced the possibility for further β-sheet structures. Overall, our results do not support a description of the B loop in group 2 HAs as a stiff spring, but, rather, it allows for more structural heterogeneity in the placement of the fusion peptides during the fusion process.

scholarly journals Plant expression systems for production of hemagglutinin as a vaccine against influenza virus.

2014 ◽  
Vol 61 (3) ◽  
Author(s):  
Patrycja Redkiewicz ◽  
Agnieszka Sirko ◽  
Katarzyna Anna Kamel ◽  
Anna Góra-Sochacka
Keyword(s):  
Influenza Virus ◽  
Large Scale ◽  
Immunological Response ◽  
Biologically Active ◽  
Scale Production ◽  
Expression Systems ◽  
Lethal Challenge ◽  
Subunit Vaccines ◽  
Large Scale Production ◽  
Major Surface

Many examples of a successful application of plant-based expression systems for production of biologically active recombinant proteins exist in the literature. These systems can function as inexpensive platforms for the large scale production of recombinant pharmaceuticals or subunit vaccines. Hemagglutinin (HA) is a major surface antigen of the influenza virus, thus it is in the centre of interests of various subunit vaccine engineering programs. Large scale production of recombinant HA in traditional expression systems, such as mammalian or insect cells, besides other limitations, is expensive and time-consuming. These difficulties stimulate an ever-increasing interest in plant-based production of this recombinant protein. Over the last few years many successful cases of HA production in plants, using both transient and stable expression systems have been reported. Various forms of recombinant HA, including monomers, trimers, virus like particles (VLPs) or chimeric proteins containing its fusion with other polypeptides were obtained and shown to maintain a proper antigenicity. Immunizations of animals (mice, ferrets, rabbits or chickens) with some of these plant-derived hemagglutinin variants were performed, and their effectiveness in induction of immunological response and protection against lethal challenge with influenza virus demonstrated. Plant-produced recombinant subunit vaccines and plant-made VLPs were successfully tested in clinical trials (Phase I and II) that confirmed their tolerance and immunogenicity.

scholarly journals Calicivirus VP2 forms a portal to mediate endosome escape

2018 ◽  
Author(s):  
Michaela Conley ◽  
Marion McElwee ◽  
Liyana Azmi ◽  
Mads Gabrielsen ◽  
Olwyn Byron ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Conformational Changes ◽  
Structural Changes ◽  
Host Cells ◽  
Major Step ◽  
Endosomal Membrane ◽  
Endosome Escape ◽  
Animal Pathogens ◽  
Capsid Shell ◽  
Capsid Protein Vp1

AbstractTo initiate the infectious process, many viruses enter their host cells by triggering endocytosis following receptor engagement. The mechanism by which non-enveloped viruses, such as the caliciviruses, escape the endosome is however poorly understood. TheCaliciviridaeinclude many important human and animal pathogens, most notably norovirus, the cause of winter vomiting disease. Here we show that VP2, a minor capsid protein encoded by all caliciviruses, forms a large portal assembly at a unique three-fold symmetry axis following receptor engagement. This feature surrounds an open pore in the capsid shell. We hypothesise that the VP2 portal complex is the means by which the virus escapes the endosome, pene-trating the endosomal membrane to release the viral genome into the cytoplasm. Cryogenic electron microscopy (cryoEM) and asymmetric reconstruction were used to investigate structural changes in the capsid of feline calicivirus (FCV) that occur when the virus binds to its cellular receptor junctional adhesion molecule-A (fJAM-A). Near atomic-resolution structures were calculated for the native virion alone and decorated with soluble receptor fragments. We present atomic models of the major capsid protein VP1 in the presence and absence of fJAM-A, revealing the contact interface and conformational changes brought about by the interaction. Furthermore, we have calculated an atomic model of the portal protein VP2 and revealed the structural changes in VP1 that lead to pore formation. While VP2 was known to be critical for the production of infectious virus, its function has been hitherto undetermined. Our finding that VP2 assembles a portal that is likely responsible for endosome escape represents a major step forward in our understanding of both theCaliciviridaeand icosahedral RNA containing viruses in general.

scholarly journals Cholera Toxin Encapsulated within Several Vibrio cholerae O1 Serotype Inaba Outer Membrane Vesicles Lacks a Functional B-Subunit

Toxins ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 207 ◽  
Author(s):  
Elnaz Rasti ◽  
Angela Brown
Keyword(s):  
Outer Membrane ◽  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Biologically Active ◽  
Host Cells ◽  
Free Form ◽  
Type Ii Secretion ◽  
Secondary Mechanism

Cholera toxin (CT), the major virulence factor of Vibrio cholerae, is an AB5 toxin secreted through the type II secretion system (T2SS). Upon secretion, the toxin initiates endocytosis through the interaction of the B pentamer with the GM1 ganglioside receptor on small intestinal cells. In addition to the release of CT in the free form, the bacteria secrete CT in association with outer membrane vesicles (OMVs). Previously, we demonstrated that strain 569B releases OMVs that encapsulate CT and which interact with host cells in a GM1-independent mechanism. Here, we have demonstrated that OMV-encapsulated CT, while biologically active, does not exist in an AB5 form; rather, the OMVs encapsulate two enzymatic A-subunit (CTA) polypeptides. We further investigated the assembly and secretion of the periplasmic CT and found that a major fraction of periplasmic CTA does not participate in the CT assembly process and instead is continuously encapsulated within the OMVs. Additionally, we found that the encapsulation of CTA fragments in OMVs is conserved among several Inaba O1 strains. We further found that under conditions in which the amount of extracellularly secreted CT increases, the concentration of OMV-encapsulated likewise CTA increases. These results point to a secondary mechanism for the secretion of biologically active CT that does not depend on the CTB-GM1 interaction for endocytosis.

scholarly journals Anatomical, morphological and phytochemical properties of Aegopodium alpestre Ledeb.: a case study of Kazakhstan

2020 ◽  
Vol 48 (3) ◽  
pp. 1473-1482
Author(s):  
Elzira A. KYRBASSOVA ◽  
Akmaral A. SARTAYEVA ◽  
Elmira M. IMANOVA ◽  
Nurdana N. SALYBEKOVA ◽  
Gulraikhan E. ZHANTEYEVA ◽  
...  
Keyword(s):  
Large Scale ◽  
Inorganic Compounds ◽  
Biologically Active Substances ◽  
Biologically Active ◽  
High Concentration ◽  
Vegetative Organs ◽  
Study Results ◽  
Cultivation Practice ◽  
Active Substances

This article deals with the phytochemical, morphological and anatomical investigation of ethanol-based extracts derived from the leaves and stems of the Aegopodium alpestre. The vegetative organs of A. alpestre were conserved according to Strasburger-Fleµming method using a 1:1:1 mixture of alcohol-glycerin-water. A total of 1200 ethanol-based extracts (2 from leaves and 2 from stem tissues per plant) were prepared using the Soxhlet extractor. All extracts were used to identify organic and inorganic compounds in the leaves and stems of the studied plant. Contents of biologically active substances, microelements, vitamins and amino acids were determined. This article is the first paper to display very high concentration and diversity of vitamins (6 types), micronutrients (5 types), and aminoacids (13 types) in the leaves and steams of A. alpestre. Findings conclude that identification of biologically active substances in the above the ground vegetative organs of A. alpestre may be a common practice in the future. Considering the study results, A. alpestre may be used as a medicinal plant on a large scale. For this, the cultivation practice needs to be scaled up.

scholarly journals Regenerative pharmacology for COPD: breathing new life into old lungs

Thorax ◽  
2019 ◽  
Vol 74 (9) ◽  
pp. 890-897 ◽  
Author(s):  
John-Poul Ng-Blichfeldt ◽  
Reinoud Gosens ◽  
Charlotte Dean ◽  
Mark Griffiths ◽  
Matthew Hind
Keyword(s):  
Large Scale ◽  
Biologically Active ◽  
Health Concern ◽  
Chronic Obstructive ◽  
Small Airways ◽  
Obstructive Pulmonary Disease ◽  
Molecular Control ◽  
Mild Disease ◽  
Peripheral Airway ◽  
Alveolar Tissue

Chronic obstructive pulmonary disease (COPD) is a major global health concern with few effective treatments. Widespread destruction of alveolar tissue contributes to impaired gas exchange in severe COPD, and recent radiological evidence suggests that destruction of small airways is a major contributor to increased peripheral airway resistance in disease. This important finding might in part explain the failure of conventional anti-inflammatory treatments to restore lung function even in patients with mild disease. There is a clear need for alternative pharmacological strategies for patients with COPD/emphysema. Proposed regenerative strategies such as cell therapy and tissue engineering are hampered by poor availability of exogenous stem cells, discouraging trial results, and risks and cost associated with surgery. An alternative therapeutic approach is augmentation of lung regeneration and/or repair by biologically active factors, which have potential to be employed on a large scale. In favour of this strategy, the healthy adult lung is known to possess a remarkable endogenous regenerative capacity. Numerous preclinical studies have shown induction of regeneration in animal models of COPD/emphysema. Here, we argue that given the widespread and irreversible nature of COPD, serious consideration of regenerative pharmacology is necessary. However, for this approach to be feasible, a better understanding of the cell-specific molecular control of regeneration, the regenerative potential of the human lung and regenerative competencies of patients with COPD are required.

Sign in / Sign up

Export Citation Format

Share Document