Pleomorphic Configuration of the Trimeric Capsid Proteins of Rice dwarf virus that Allows Formation of Both the Outer Capsid and Tubular Crystals

Iwasaki, Katsunori; Miyazaki, Naoyuki; Hammar, Lena Marmstål; Zhu, Yong; Omura, Toshihiro; Wu, Bomu; Sjöborg, Fredrik; Yonekura, Koji; Murata, Kazuyoshi; Namba, Keiichi; Caspar, D. L. D.; Fujiyoshi, Yoshinori; Cheng, R. Holland

doi:10.1016/j.jmb.2008.08.021

Cited by 9 publications

(8 citation statements)

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“…As described in previous studies (16,32), the overall structure of RDV is more like a pronounced polyhedron, unlike other reoviruses such as rotavirus (38) and bluetongue virus (31) that have spherical core particles. The overall polyhedral shape of RDV is caused by the shape of the outer surface of the inner capsid layer of the P3 protein, which forms the flat surface around the icosahedral 3-fold axis and protrudes around the icosahedral 5-fold axis.…”

Section: Regulation Of the Spatial Arrangement Of P2 Proteinsmentioning

confidence: 57%

“…(c) Interactions between P8 trimers. There are seven kinds of interactions between P8 trimers in the outer capsid shell of RDV (32). Side views of contacts between adjacent P8 trimers (P-P and S-S contacts among them) are shown.…”

Section: Discussionmentioning

confidence: 99%

“…The P-P contacts deviate markedly from other contacts since they have a large convex tilt angle. The upper domains of adjacent P trimers are more distantly separated from each other, with a tilt angle of $41 as described previously (32). (d) Schematic representation of the P2 binding mechanism around icosahedral 5-fold axes.…”

Section: Discussionmentioning

confidence: 99%

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Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 ofRice dwarf viruslocated around the icosahedral 5-fold axes

Miyazaki

Higashiura

et al. 2015

J Biochem

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The minor outer capsid protein P2 of Rice dwarf virus (RDV), a member of the genus Phytoreovirus in the family Reoviridae, is essential for viral cell entry. Here, we clarified the structure of P2 and the interactions to host insect cells. Negative stain electron microscopy (EM) showed that P2 proteins are monomeric and flexible L-shaped filamentous structures of $20 nm in length. Cryo-EM structure revealed the spatial arrangement of P2 in the capsid, which was prescribed by the characteristic virion structure. The P2 proteins were visualized as partial rod-shaped structures of $10 nm in length in the cryo-EM map and accommodated in crevasses on the viral surface around icosahedral 5-fold axes with hydrophobic interactions. The remaining disordered region of P2 assumed to be extended to the radial direction towards exterior. Electron tomography clearly showed that RDV particles were away from the cellular membrane at a uniform distance and several spike-like densities, probably corresponding to P2, connecting a viral particle to the host cellular membrane during cell entry. By combining the in vitro and in vivo structural information, we could gain new insights into the detailed mechanism of the cell entry of RDV.Keywords: cryo-electron microscopy/electron tomography/Phytoreovirus/Rice dwarf virus/viral cell entry.Abbreviations: CCD, charge-coupled device; CPV, Cytoplasmic polyhedrosis virus; cryo-EM, cryoelectron microscopy; dsRNA, double-stranded RNA; RDV, Rice dwarf virus; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; 3D, threedimensional.Reoviridae is the largest and most diverse family of non-enveloped double-stranded RNA (dsRNA) viruses, infecting plants, vertebrates, insects and fungi (1). Except for the single-layered Cytoplasmic polyhedrosis virus (CPV), all known reoviruses have two or three multi-layered capsids of 6080 nm in diameter. The capsid shells enclose segmented dsRNA as a viral genome and their own transcriptional enzymes. They have the conserved innermost capsid shells in spite of the absence of sequence homology, while the outer capsid shells including the cell attachment proteins exhibit diverse morphologies among viruses of different genera. This is probably related to the wide range of host species associated with the different host-cell recognition mechanisms among the reoviruses (2, 3). Viral cell attachment to the host cell surface, mediated mostly through specific molecules, is required for the successful adsorption and subsequent entry of the virus into the host cell for viral replication. To understand the molecular mechanisms of how viruses infect and replicate in cells, structural information on the viruses and the molecular interactions between the viral and cellular factors are essential. Several structures of viral cell attachment proteins (4, 5) and the formation of membrane pores by viral cell-penetration proteins (6, 7) are known for animal reoviruses. However, little or no knowledge is available so far regarding the cell attachment and entry mechani...

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Section: Regulation Of the Spatial Arrangement Of P2 Proteinsmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

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Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 ofRice dwarf viruslocated around the icosahedral 5-fold axes

Miyazaki

Higashiura

et al. 2015

J Biochem

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“…Some viruses, such as human immunodeficiency virus (HIV), 138 Rice dwarf virus (RDV), 139 and coronavirus spike protein 140 adopt trimer intermediates in the formation of their capsids from numbers of identical subunits. Although E2 protein cage and viral capsids have neither sequence homology nor natural function in common, the virus-like E2 protein cage are structural parallel to viral particles with dodecahedral symmetry.…”

Section: Introductionmentioning

confidence: 99%

“…Comparison between the disruptive effects from intra-and inter-trimer interfaces suggests that trimers might be present as a basic building block to form the fully assembled virus-like E2 protein. Some virus, such as human immunodeficiency virus (HIV),138 Rice dwarf virus (RDV),139 and coronavirus spike protein140 adopt trimer intermediate in the formation of their capsids.…”

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Understanding the self-assembly mechanism of E2 protein cage and exploring its potential applications

Peng¹

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Dihydrolipoamide acetyltransferase (E2 protein) is part of pyruvate dehydrogenase multi-enzyme complex from Bacillus stearothermophilus. However, we don't consider its enzymatic activity in this work. E2 protein used in this work is a protein cage derived and is composed of 60 subunits. Structurally, the 60 subunits selfassemble to form a 25-nm hollow caged structure. Previous works have demonstrated its potential application as nanocapsule in drug delivery to encapsulate small molecules in its inner cavity, i.e. cancer drugs. The researches that we have been done in this work are summarized as followings: To better control the release of the encapsulated drugs at target sites during drug delivery, modulating the self-assembly process of E2 protein under different environmental stimuli is desirable. Therefore, understanding of the self-assembly mechanism of E2 protein is required. By truncating the C-terminal α-helix of E2 protein, the association between trimeric structures are eliminated and the selfassembly was halted at the trimer intermediate state. Molecular dynamic simulation reaffirms that the E2 protein adopts trimer intermediate prior to its fully assembled caged structure and that the C-terminus plays a critical role in mediating the selfassembly from monomer to trimer and to 60-mer. Upon identifying the importance of the C-terminus in the trimer and subsequently the cage assembly, other functionalities were introduced to enhance the release of molecular cargos (e.g. cancer drugs) from the cavity of the E2 protein cage. To this goal, amino acid histidines are introduced at critical sites at the interfaces between trimer structures. Histidine has a unique property that it is charged at acidic pH while VI remains uncharged at neutral and basic pH-s. The proximity of two or more histidines at the subunit interfaces induces repulsion and hence their separation at acidic pH, subsequently leading to the soluble and non-denatured disassembly of the E2 protein. Incorporation of a unique GALA peptide (peptide with repeating amino acids: Glu-Ala-Leu-Ala) with pH-sensitive helix-to-coil transition at low and high pH, respectively, to substitute the original C-terminal α-helix induces an interesting assembly characteristic. As a result, the self-assembly of E2 protein become pHresponsive and present in inversed direction. At neutral or high pH-s, the extended random coil state of GALA peptide dissociates the E2 protein cage. As the pH is lowered, E2 protein reassembled due to the formation of α-helix from GALA peptide. Moreover, the pH-inducible self-assembly of this engineered E2 protein is reversible. The well-defined inner cavity provides the possibility to utilize the E2 protein cage as a nanoreactor for inorganic nanoparticle synthesis for potential application as an imaging contrast agent. Iron-binding peptides were incorporated to the interior surface of E2 protein without jeopardizing its self-assembly and caged structure. The engineered proteins are able to nucleate irons. The subsequent oxidation of the ...

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Assembly of Large Icosahedral Double-Stranded RNA Viruses

Poranen

Bamford

2011

Advances in Experimental Medicine and Biology

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Double-stranded RNA (dsRNA) viruses are a diverse group of viruses infecting hosts from bacteria to higher eukaryotes. Among the hosts are humans, domestic animals, and economically important plant species. Fine details of high-resolution virion structures have revealed common structural characteristics unique to these viruses including an internal icosahedral capsid built from 60 asymmetric dimers (120 monomers!) of the major coat protein. Here we focus mainly on the structures and assembly principles of large icosahedral dsRNA viruses belonging to the families of Cystoviridae and Reoviridae. It is obvious that there are a variety of assembly pathways utilized by different viruses starting from similar building blocks and reaching in all cases a similar capsid architecture. This is true even with closely related viruses indicating that the assembly pathway per se is not an indicator of relatedness and is achieved with minor changes in the interacting components.

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Pleomorphic Configuration of the Trimeric Capsid Proteins of Rice dwarf virus that Allows Formation of Both the Outer Capsid and Tubular Crystals

Cited by 9 publications

References 40 publications

Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 ofRice dwarf viruslocated around the icosahedral 5-fold axes

Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 ofRice dwarf viruslocated around the icosahedral 5-fold axes

Understanding the self-assembly mechanism of E2 protein cage and exploring its potential applications

Assembly of Large Icosahedral Double-Stranded RNA Viruses

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