scholarly journals Structure and assembly of phage Φ29

1976 ◽  
Vol 276 (943) ◽  
pp. 29-35 ◽  
Keyword(s):  
Molecular Mass ◽  
Capsid Protein ◽  
Scaffolding Protein ◽  
Structural Proteins ◽  
Icosahedral Symmetry ◽  
Gene Products ◽  
Structural Protein ◽  
End Caps ◽  
Normal Shape

Bacteriophage Φ29 is a small, morphologically complex, virus with a DNA of molecular mass 12 x 10 6 . The most likely structure of the head of Φ29 consists of two fivefold symmetric end-caps based on T = 1 icosahedral symmetry, separated by an equatorial row of 5 hexamers. The eighteen genes identified in Φ29 genome have been mapped and, in some cases, the gene products have been identified. Five linked genes, four coding for structural proteins (G, A, E, H) and one coding for a non-structural protein (J), are essential to determine the normal shape of the capsid. Protein pJ may be a scaffolding protein. An account of the effects of mutations in Φ29 genes is given.

scholarly journals Infectious Bursal Disease Virus Capsid Assembly and Maturation by Structural Rearrangements of a Transient Molecular Switch

2007 ◽  
Vol 81 (13) ◽  
pp. 6869-6878 ◽  
Author(s):  
Daniel Luque ◽  
Irene Saugar ◽  
José F. Rodríguez ◽  
Nuria Verdaguer ◽  
Damiá Garriga ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Disease Virus ◽  
Infectious Bursal Disease Virus ◽  
Scaffolding Protein ◽  
Infectious Bursal Disease ◽  
Capsid Assembly ◽  
Protein Oligomerization ◽  
Structural Protein ◽  
Bursal Disease ◽  
Α Helix

ABSTRACT Infectious bursal disease virus (IBDV), a double-stranded RNA (dsRNA) virus belonging to the Birnaviridae family, is an economically important avian pathogen. The IBDV capsid is based on a single-shelled T=13 lattice, and the only structural subunits are VP2 trimers. During capsid assembly, VP2 is synthesized as a protein precursor, called pVP2, whose 71-residue C-terminal end is proteolytically processed. The conformational flexibility of pVP2 is due to an amphipathic α-helix located at its C-terminal end. VP3, the other IBDV major structural protein that accomplishes numerous roles during the viral cycle, acts as a scaffolding protein required for assembly control. Here we address the molecular mechanism that defines the multimeric state of the capsid protein as hexamers or pentamers. We used a combination of three-dimensional cryo-electron microscopy maps at or close to subnanometer resolution with atomic models. Our studies suggest that the key polypeptide element, the C-terminal amphipathic α-helix, which acts as a transient conformational switch, is bound to the flexible VP2 C-terminal end. In addition, capsid protein oligomerization is also controlled by the progressive trimming of its C-terminal domain. The coordination of these molecular events correlates viral capsid assembly with different conformations of the amphipathic α-helix in the precursor capsid, as a five-α-helix bundle at the pentamers or an open star-like conformation at the hexamers. These results, reminiscent of the assembly pathway of positive single-stranded RNA viruses, such as nodavirus and tetravirus, add new insights into the evolutionary relationships of dsRNA viruses.

scholarly journals Characterization of a Rhesus Monkey Calicivirus Representing a New Genus of Caliciviridae

2008 ◽  
Vol 82 (11) ◽  
pp. 5408-5416 ◽  
Author(s):  
Tibor Farkas ◽  
Karol Sestak ◽  
Chao Wei ◽  
Xi Jiang
Keyword(s):  
Molecular Mass ◽  
Capsid Protein ◽  
Phylogenetic Trees ◽  
Rhesus Macaques ◽  
Buoyant Density ◽  
Primate Research ◽  
Structural Protein ◽  
Calculated Molecular Mass ◽  
Genetic Characteristics

ABSTRACT In this study, we report the characterization of a novel calicivirus (CV), the Tulane virus (TV), which was isolated from stool samples of captive juvenile rhesus macaques (Macaca mulatta) of the Tulane National Primate Research Center. The complete genome of TV contains 6,714 nucleotides plus a poly(A) tail and is organized into three open reading frames (ORFs) that encode the nonstructural (NS) polyprotein (ORF1); the capsid protein (ORF2), with an estimated molecular mass of 57.9 kDa; and a possible minor structural protein (ORF3), with an isoelectric point (pI) of 10.0 and a calculated molecular mass of 22.8 kDa. The NS polyprotein revealed all typical CV amino acid motifs, including GXXGXGKT (NTPase), EYXEX (Vpg), GDCG (protease), and GLPSG and YGDD (polymerase). Phylogenetic trees constructed for the NS polyprotein, NTPase, protease, polymerase, and capsid protein sequences consistently placed the TV on a branch rooted with Norovirus, but with distances equal to those between other genera. The TV can be cultured in a monkey kidney cell line (LLC-MK2) with the appearance of typical cytopathic effect. TV exhibits a typical CV morphology, with a diameter of 36 nm, and has a buoyant density of 1.37 g/ml. According to these physicochemical and genetic characteristics, TV represents a new CV genus for which we propose the name “Recovirus” (rhesus enteric CV). Although the pathogenicity of TV in rhesus macaques remains to be elucidated, the likelihood of TV causing intestinal infection and the availability of a tissue culture system make this virus a valuable surrogate for human CVs.

scholarly journals Identification of the ral and rac1 Gene Products, Low Molecular Mass GTP-binding Proteins from Human Platelets

1989 ◽  
Vol 264 (28) ◽  
pp. 16383-16389
Author(s):  
P G Polakis ◽  
R F Weber ◽  
B Nevins ◽  
J R Didsbury ◽  
T Evans ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Binding Proteins ◽  
Human Platelets ◽  
Gene Products ◽  
Gtp Binding Proteins ◽  
Gtp Binding

scholarly journals Open reading frame 2 of porcine circovirus type 2 encodes a major capsid protein

2000 ◽  
Vol 81 (9) ◽  
pp. 2281-2287 ◽  
Author(s):  
Porntippa Nawagitgul ◽  
Igor Morozov ◽  
Steven R. Bolin ◽  
Perry A. Harms ◽  
Steven D. Sorden ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Gene Product ◽  
Protein S ◽  
Basic Amino Acid ◽  
Porcine Circovirus Type ◽  
Open Reading Frames ◽  
Porcine Circovirus ◽  
Structural Protein ◽  
Major Structural Protein ◽  
Orf2 Protein

Porcine circovirus 2 (PCV2), a single-stranded DNA virus associated with post-weaning multisystemic wasting syndrome of swine, has two potential open reading frames, ORF1 and ORF2, greater than 600 nucleotides in length. ORF1 is predicted to encode a replication-associated protein (Rep) essential for replication of viral DNA, while ORF2 contains a conserved basic amino acid sequence at the N terminus resembling that of the major structural protein of chicken anaemia virus. Thus far, the structural protein(s) of PCV2 have not been identified. In this study, a viral structural protein of 30 kDa was identified in purified PCV2 particles. ORF2 of PCV2 was cloned into a baculovirus expression vector and the gene product was expressed in insect cells. The expressed ORF2 gene product had a molecular mass of 30 kDa, similar to that detected in purified virus particles. The recombinant ORF2 protein self-assembled to form capsid-like particles when viewed by electron microscopy. Antibodies against the ORF2 protein were detected in samples of sera obtained from pigs as early as 3 weeks after experimental infection with PCV2. These results show that the major structural protein of PCV2 is encoded by ORF2 and has a molecular mass of 30 kDa.

scholarly journals Role of Structural and Non-Structural Proteins and Therapeutic Targets of SARS-CoV-2 for COVID-19

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 821
Author(s):  
Rohitash Yadav ◽  
Jitendra Kumar Chaudhary ◽  
Neeraj Jain ◽  
Pankaj Kumar Chaudhary ◽  
Supriya Khanra ◽  
...  
Keyword(s):  
Host Cell ◽  
Protein S ◽  
Structural Similarity ◽  
Cell Receptor ◽  
Molecular Assembly ◽  
The Body ◽  
Spike Protein ◽  
Structural Proteins ◽  
Structural Protein ◽  
Novel Coronavirus

Coronavirus belongs to the family of Coronaviridae, comprising single-stranded, positive-sense RNA genome (+ ssRNA) of around 26 to 32 kilobases, and has been known to cause infection to a myriad of mammalian hosts, such as humans, cats, bats, civets, dogs, and camels with varied consequences in terms of death and debilitation. Strikingly, novel coronavirus (2019-nCoV), later renamed as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), and found to be the causative agent of coronavirus disease-19 (COVID-19), shows 88% of sequence identity with bat-SL-CoVZC45 and bat-SL-CoVZXC21, 79% with SARS-CoV and 50% with MERS-CoV, respectively. Despite key amino acid residual variability, there is an incredible structural similarity between the receptor binding domain (RBD) of spike protein (S) of SARS-CoV-2 and SARS-CoV. During infection, spike protein of SARS-CoV-2 compared to SARS-CoV displays 10–20 times greater affinity for its cognate host cell receptor, angiotensin-converting enzyme 2 (ACE2), leading proteolytic cleavage of S protein by transmembrane protease serine 2 (TMPRSS2). Following cellular entry, the ORF-1a and ORF-1ab, located downstream to 5′ end of + ssRNA genome, undergo translation, thereby forming two large polyproteins, pp1a and pp1ab. These polyproteins, following protease-induced cleavage and molecular assembly, form functional viral RNA polymerase, also referred to as replicase. Thereafter, uninterrupted orchestrated replication-transcription molecular events lead to the synthesis of multiple nested sets of subgenomic mRNAs (sgRNAs), which are finally translated to several structural and accessory proteins participating in structure formation and various molecular functions of virus, respectively. These multiple structural proteins assemble and encapsulate genomic RNA (gRNA), resulting in numerous viral progenies, which eventually exit the host cell, and spread infection to rest of the body. In this review, we primarily focus on genomic organization, structural and non-structural protein components, and potential prospective molecular targets for development of therapeutic drugs, convalescent plasm therapy, and a myriad of potential vaccines to tackle SARS-CoV-2 infection.

scholarly journals Cryo-EM structure of the bacteriophage T4 isometric head at 3.3-Å resolution and its relevance to the assembly of icosahedral viruses

2017 ◽  
Vol 114 (39) ◽  
pp. E8184-E8193 ◽  
Author(s):  
Zhenguo Chen ◽  
Lei Sun ◽  
Zhihong Zhang ◽  
Andrei Fokine ◽  
Victor Padilla-Sanchez ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Major Capsid Protein ◽  
Bacteriophage T4 ◽  
Hexagonal Lattice ◽  
Scaffolding Proteins ◽  
Outer Capsid Protein ◽  
Head Assembly ◽  
Icosahedral Viruses ◽  
End Caps ◽  
Outer Capsid

The 3.3-Å cryo-EM structure of the 860-Å-diameter isometric mutant bacteriophage T4 capsid has been determined. WT T4 has a prolate capsid characterized by triangulation numbers (T numbers) Tend= 13 for end caps and Tmid= 20 for midsection. A mutation in the major capsid protein, gp23, produced T=13 icosahedral capsids. The capsid is stabilized by 660 copies of the outer capsid protein, Soc, which clamp adjacent gp23 hexamers. The occupancies of Soc molecules are proportional to the size of the angle between the planes of adjacent hexameric capsomers. The angle between adjacent hexameric capsomers is greatest around the fivefold vertices, where there is the largest deviation from a planar hexagonal array. Thus, the Soc molecules reinforce the structure where there is the greatest strain in the gp23 hexagonal lattice. Mutations that change the angles between adjacent capsomers affect the positions of the pentameric vertices, resulting in different triangulation numbers in bacteriophage T4. The analysis of the T4 mutant head assembly gives guidance to how other icosahedral viruses reproducibly assemble into capsids with a predetermined T number, although the influence of scaffolding proteins is also important.

scholarly journals Rubella Virus E2 Signal Peptide Is Required for Perinuclear Localization of Capsid Protein and Virus Assembly

2001 ◽  
Vol 75 (4) ◽  
pp. 1978-1983 ◽  
Author(s):  
Lok Man J. Law ◽  
Robert Duncan ◽  
Ali Esmaili ◽  
Hira L. Nakhasi ◽  
Tom C. Hobman
Keyword(s):  
Endoplasmic Reticulum ◽  
Capsid Protein ◽  
Signal Peptide ◽  
Rubella Virus ◽  
Virus Assembly ◽  
Signal Peptidase ◽  
Structural Proteins ◽  
Carboxy Terminus ◽  
Membrane Anchor ◽  
Polyprotein Precursor

ABSTRACT The rubella virus (RV) structural proteins capsid, E2, and E1 are synthesized as a polyprotein precursor. The signal peptide that initiates translocation of E2 into the lumen of the endoplasmic reticulum remains attached to the carboxy terminus of the capsid protein after cleavage by signal peptidase. Among togaviruses, this feature is unique to RV. The E2 signal peptide has previously been shown to function as a membrane anchor for the capsid protein. In the present study, we demonstrate that this domain is required for RV glycoprotein-dependent localization of the capsid protein to the juxtanuclear region and subsequent virus assembly at the Golgi complex.

scholarly journals Minor structural protein VP2 in rabbit hemorrhagic disease virus downregulates the expression of the viral capsid protein VP60

2009 ◽  
Vol 90 (12) ◽  
pp. 2952-2955 ◽  
Author(s):  
Liu Chen ◽  
Guangqing Liu ◽  
Zheng Ni ◽  
Bin Yu ◽  
Tao Yun ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Disease Virus ◽  
Luciferase Assay ◽  
Rabbit Hemorrhagic Disease Virus ◽  
Hemorrhagic Disease ◽  
Mrna Levels ◽  
Structural Protein ◽  
Rabbit Hemorrhagic Disease ◽  
Minor Structural Protein ◽  
Capsid Protein Vp60

Rabbit hemorrhagic disease virus (RHDV) has two structural proteins: the major capsid protein VP60 and the minor capsid protein VP2. VP2 is speculated to play an important role in the virus life cycle. To investigate the effect of VP2 on VP60 expression, three types of experiment (baculovirus–insect cell system, mammalian–luciferase assay system and in vitro coupled transcription/translation system) were used to express VP60 alone or co-expressed with VP2. Both forms of VP60 were able to form virus-like particles in insect cells. Western blot analysis and dual-luciferase assays demonstrated that the presence of VP2 results in downregulation of the expression of VP60 in vivo. Real-time RT-PCR of mRNA levels showed that downregulation of VP60 occurs at the transcriptional level. The ability of the viral minor structural protein VP2 to regulate capsid protein levels may contribute to effective virus infection.

The subcellular distribution of the high molecular mass protein, HD1, is determined by the cytoplasmic domain of the integrin beta 4 subunit

1997 ◽  
Vol 110 (2) ◽  
pp. 169-178 ◽  
Author(s):  
P. Sanchez-Aparicio ◽  
A.M. Martinez de Velasco ◽  
C.M. Niessen ◽  
L. Borradori ◽  
I. Kuikman ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Subcellular Distribution ◽  
Cytoplasmic Domain ◽  
High Molecular Mass ◽  
Integrin Subunit ◽  
Type Ii ◽  
Structural Protein ◽  
Focal Contacts ◽  
Cell Substrate ◽  
Beta 1 Integrin

The high molecular mass protein, HD1, is a structural protein present in hemidesmosomes as well as in distinct adhesion structures termed type II hemidesmosomes. We have studied the distribution and expression of HD1 in the GD25 cells, derived from murine embryonal stem cells deficient for the beta 1 integrin subunit. We report here that these cells possess HD1 but not BP230 or BP180; two other hemidesmosomal constituents, and express only traces of the alpha 6 beta 4 integrin. By immunofluorescence and interference reflection microscopy HD1 was found together with vinculin at the end of actin filaments in focal contacts. In OVCAR-4 cells, derived from a human ovarian carcinoma which, like GD25 cells, only weakly express alpha 6 beta 4, HD1 was also localized in focal contacts. Upon transfection of both GD25 and OVCAR-4 cells with cDNA for the human beta 4 subunit the subcellular distribution of HD1 changed significantly. HD1 is then no longer present in focal contacts but in other structures at cell-substrate contacts, colocalized with alpha 6 beta 4. These junctional complexes are probably the equivalent of the type II hemidesmosomes. Transfection of GD25 cells with beta 1 cDNA did not affect the distribution of HD1, which indicates that the localization of HD1 in focal contacts was not due to the absence of beta 1. Moreover, in GD25 cells transfected with cDNA encoding a beta 4/beta 1 chimera, in which the cytoplasmic domain of beta 4 was replaced by that of beta 1, the distribution of HD1 was unaffected. Our findings indicate that the cytoplasmic domain of beta 4 determines the subcellular distribution of HD1 and emphasize the important role of alpha 6 beta 4 in the assembly of hemidesmosomes and other junctional adhesive complexes containing HD1.

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