scholarly journals The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell

Viruses ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 910
Author(s):  
J. Bernard Heymann ◽  
Bing Wang ◽  
William W. Newcomb ◽  
Weimin Wu ◽  
Dennis C. Winkler ◽  
...  
Keyword(s):  
Major Capsid Protein ◽  
Protease Gene ◽  
Lattice Structures ◽  
Asymmetric Unit ◽  
Amber Mutation ◽  
Viral Protease ◽  
Virion Assembly ◽  
Cell Lysate ◽  
Tetragonal Lattice ◽  
Giant Viruses

“Giant” phages have genomes of >200 kbp, confined in correspondingly large capsids whose assembly and maturation are still poorly understood. Nevertheless, the first assembly product is likely to be, as in other tailed phages, a procapsid that subsequently matures and packages the DNA. The associated transformations include the cleavage of many proteins by the phage-encoded protease, as well as the thinning and angularization of the capsid. We exploited an amber mutation in the viral protease gene of the Salmonella giant phage SPN3US, which leads to the accumulation of a population of capsids with distinctive properties. Cryo-electron micrographs reveal patterns of internal density different from those of the DNA-filled heads of virions, leading us to call them “mottled capsids”. Reconstructions show an outer shell with T = 27 symmetry, an embellishment of the HK97 prototype composed of the major capsid protein, gp75, which is similar to some other giant viruses. The mottled capsid has a T = 1 inner icosahedral shell that is a complex network of loosely connected densities composed mainly of the ejection proteins gp53 and gp54. Segmentation of this inner shell indicated that a number of densities (~12 per asymmetric unit) adopt a “twisted hook” conformation. Large patches of a proteinaceous tetragonal lattice with a 67 Å repeat were also present in the cell lysate. The unexpected nature of these novel inner shell and lattice structures poses questions as to their functions in virion assembly.

scholarly journals A Newly Isolated Reovirus Has the Simplest Genomic and Structural Organization of Any Reovirus

2014 ◽  
Vol 89 (1) ◽  
pp. 676-687 ◽  
Author(s):  
Albert J. Auguste ◽  
Jason T. Kaelber ◽  
Eric B. Fokam ◽  
Hilda Guzman ◽  
Christine V. F. Carrington ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Major Capsid Protein ◽  
Structural Characteristics ◽  
Infected Cell Line ◽  
Asymmetric Unit ◽  
Loss Of Function ◽  
Content Type ◽  
Mosquito Cells ◽  
A Genome ◽  
Pathogenic Viruses

ABSTRACTA total of 2,691 mosquitoes representing 17 species was collected from eight locations in southwest Cameroon and screened for pathogenic viruses. Ten isolates of a novel reovirus (genusDinovernavirus) were detected by culturing mosquito pools onAedes albopictus(C6/36) cell cultures. A virus that caused overt cytopathic effects was isolated, but it did not infect vertebrate cells or produce detectable disease in infant mice after intracerebral inoculation. The virus, tentatively designated Fako virus (FAKV), represents the first 9-segment, double-stranded RNA (dsRNA) virus to be isolated in nature. FAKV appears to have a broad mosquito host range, and its detection in male specimens suggests mosquito-to-mosquito transmission in nature. The structure of the T=1 FAKV virion, determined to subnanometer resolution by cryoelectron microscopy (cryo-EM), showed only four proteins per icosahedral asymmetric unit: a dimer of the major capsid protein, one turret protein, and one clamp protein. While all other turreted reoviruses of known structures have at least two copies of the clamp protein per asymmetric unit, FAKV's clamp protein bound at only one conformer of the major capsid protein. The FAKV capsid architecture and genome organization represent the most simplified reovirus described to date, and phylogenetic analysis suggests that it arose from a more complex ancestor by serial loss-of-function events.IMPORTANCEWe describe the detection, genetic, phenotypic, and structural characteristics of a novelDinovernavirusspecies isolated from mosquitoes collected in Cameroon. The virus, tentatively designated Fako virus (FAKV), is related to both single-shelled and partially double-shelled viruses. The only other described virus in this genus was isolated from cultured mosquito cells. It was previously unclear whether the phenotypic characteristics of that virus were reflective of this genus in nature or were altered during serial passaging in the chronically infected cell line. FAKV is a naturally occurring single-shelled reovirus with a unique virion architecture that lacks several key structural elements thought to stabilize a single-shelled reovirus virion, suggesting what may be the minimal number of proteins needed to form a viable reovirus particle. FAKV evolved from more complex ancestors by losing a genome segment and several virion proteins.

scholarly journals The 4.4 Å structure of the giant Melbournevirus virion belonging to the Marseilleviridae family

2021 ◽  
Author(s):  
Raymond N Burton-Smith ◽  
Hemanth K N Reddy ◽  
Martin Svenda ◽  
Chantal Abergel ◽  
Kenta Okamoto ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Capsid Protein ◽  
Major Capsid Protein ◽  
Capsid Proteins ◽  
Atomic Model ◽  
Penton Base ◽  
Cryo Electron Microscopy ◽  
Internal Membrane ◽  
Structural Details ◽  
Giant Viruses

Members of Marseilleviridae, one family of icosahedral giant viruses classified in 2012 have been identified worldwide in all types of environments. The virion shows a characteristic internal membrane extrusion at the five-fold vertices of the capsid, but its structural details need to be elucidated. We now report the 4.4 Å cryo-electron microscopy structure of the Melbournevirus capsid. An atomic model of the major capsid protein (MCP) shows a unique cup structure on the trimer that accommodates additional proteins. A polyalanine model of the penton base protein shows internally extended N- and C-terminals, which indirectly connect to the internal membrane extrusion. The Marseilleviruses share the same orientational organisation of the MCPs as PBCV-1 and CroV, but do not appear to possess a protein akin to the ″tape measure″ of these viruses. Minor capsid proteins named PC-β, zipper, and scaffold are proposed to control the dimensions of the capsid during assembly.

scholarly journals Hsp90 is involved in pseudorabies virus virion assembly via stabilizing major capsid protein VP5

Virology ◽  
2021 ◽  
Vol 553 ◽  
pp. 70-80
Author(s):  
Wen-Jing Zhang ◽  
Ren-Qi Wang ◽  
Lin-Tao Li ◽  
Wen Fu ◽  
Huan-Chun Chen ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Pseudorabies Virus ◽  
Major Capsid Protein ◽  
Virion Assembly

Novel two-dimensional ZnO$_2$, CdO$_2$ and HgO$_2$ monolayers: a first-principles-based prediction

2021 ◽  
Author(s):  
Mehrdad Faraji ◽  
Asadollah Bafekry ◽  
Daniela Gogova ◽  
Hoat Do Minh ◽  
Mitra Ghergherehchi ◽  
...  
Keyword(s):  
First Principles ◽  
Lattice Structures ◽  
Two Dimensional ◽  
Chemical Formula ◽  
Tetragonal Lattice

In this paper, the existence of monolayers with the chemical formula XO$_2$, where X= Zn, Cd, and Hg with hexagonal and tetragonal lattice structures is theoretically predicted by means of...

Examination of Rabbit Fc Crystals

1968 ◽  
Vol 26 ◽  
pp. 140-141
Author(s):  
J. P. Robinson ◽  
P. G. Lenhert
Keyword(s):  
Molecular Weight ◽  
Flat Plate ◽  
Phosphate Buffer ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutral Ph ◽  
Small Crystals ◽  
Carbon Coated ◽  
Diffraction Patterns

Crystallographic studies of rabbit Fc using X-ray diffraction patterns were recently reported. The unit cell constants were reported to be a = 69. 2 A°, b = 73. 1 A°, c = 60. 6 A°, B = 104° 30', space group P21, monoclinic, volume of asymmetric unit V = 148, 000 A°3. The molecular weight of the fragment was determined to be 55, 000 ± 2000 which is in agreement with earlier determinations by other methods.Fc crystals were formed in water or dilute phosphate buffer at neutral pH. The resulting crystal was a flat plate as previously described. Preparations of small crystals were negatively stained by mixing the suspension with equal volumes of 2% silicotungstate at neutral pH. A drop of the mixture was placed on a carbon coated grid and allowed to stand for a few minutes. The excess liquid was removed and the grid was immediately put in the microscope.

Backscattered Electron Imaging of GaAs/AlGaAs Super Lattice Structures with an Ultra-High- Resolution SEM

1988 ◽  
Vol 46 ◽  
pp. 204-205
Author(s):  
Kazumichi Ogura ◽  
Michael M. Kersker
Keyword(s):  
High Resolution ◽  
Layer Structure ◽  
High Sensitivity ◽  
Beam Current ◽  
Electron Beam Current ◽  
Lattice Structures ◽  
Super Lattice ◽  
Different Types ◽  
Backscattered Electron ◽  
Electron Imaging

Backscattered electron (BE) images of GaAs/AlGaAs super lattice structures were observed with an ultra high resolution (UHR) SEM JSM-890 with an ultra high sensitivity BE detector. Three different types of super lattice structures of GaAs/AlGaAs were examined. Each GaAs/AlGaAs wafer was cleaved by a razor after it was heated for approximately 1 minute and its crosssectional plane was observed.First, a multi-layer structure of GaAs (100nm)/AlGaAs (lOOnm) where A1 content was successively changed from 0.4 to 0.03 was observed. Figures 1 (a) and (b) are BE images taken at an accelerating voltage of 15kV with an electron beam current of 20pA. Figure 1 (c) is a sketch of this multi-layer structure corresponding to the BE images. The various layers are clearly observed. The differences in A1 content between A1 0.35 Ga 0.65 As, A1 0.4 Ga 0.6 As, and A1 0.31 Ga 0.69 As were clearly observed in the contrast of the BE image.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

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