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PubMed1997

The PI capsid region of Theiler's virus controls replication in mouse glial cell cultures.

The GDVII strain of Theiler's virus is virulent. The DA strain is avirulent and can persist and initiate lesions of inflammatory demyelination in the CNS of susceptible strains of mice. Other, resistant strains of mice clear the infection. Replication of the GDVII and DA strains of Theiler's virus and their genetic recombinants R2, R3 and R4 were compared in mixed glial cell cultures derived from the mouse CNS. Differences were observed in the early rate of viral production. These mapped to the P1 capsid region of the viral genome. Viruses with GDVII P1 sequences produced virus and spread more rapidly than viruses with DA P1 sequences. GDVII virus infected greater numbers of cells than DA virus. Both strains of virus rapidly replicated at least to the level of translation in astrocytes (GFAP+), macrophage/microglial cells (F4/80+), oligodendrocytes (O4+) and bipotential precursor (A2B5+) cells. Early in infection many A2B5+ and GFAP+ cells were infected and destroyed. In contrast, O4+ cells were relatively resistant to cell-death. The cultures survived and produced virus over 14 days of study, at which time all 4 cell-type were present in the culture but < 1% of all the cells, the majority of which were O4+, expressed viral protein. Most of these infected O4+ cells retained a healthy morphology with extensive sheets of cytoplasm, suggesting that Theiler's virus infection of mature oligodendrocytes was non-destructive.

Animals↗
PubMed1998

Detection and strain differentiation of feline calicivirus in conjunctival swabs by RT-PCR of the hypervariable region of the capsid protein gene.

Reverse transcription-polymerase chain reaction (RT-PCR) was used to direct the amplification of a 670 to 680 base pair segment that included the hypervariable regions of the capsid protein gene of feline calicivirus (FCV). The segment was amplified from 13/13 cultivated FCV strains including 12 field isolates collected over 18 years. The sensitivities of culture and this RT-PCR for the detection of FCV in conjunctival swabs over the course of infection were then compared and correlated with clinical signs in 5 vaccinated and 3 unvaccinated experimentally-infected cats. Conjunctival swabs were taken daily from days 0 to 14 and on days 16, 19, 21 and 24 after challenge. FCV was detected in 19/144 swabs by RT-PCR and 16/144 swabs by culture. Virus detection correlated poorly with clinical signs regardless of the assay used. The Sau3AI restriction profiles of the RT-PCR products amplified from both cultivated strains and clinical samples were compared. All 13 cultivated isolates, including the 12 field isolates, exhibited different profiles, whereas all profiles from the experimentally-infected cats were identical, and matched the profile of the challenge/vaccine strain. This study has established that the RT-PCR assay described is as sensitive as culture for detection of FCV in conjunctival swabs, that a broad range of field isolates can be detected and rapidly differentiated by restriction endonuclease digestion, and that the assay thus meets the requirements for large scale epidemiological studies of FCV infections in cats. However, it has also shown that even the use of RT-PCR on conjunctival swabs alone is insufficient for accurate diagnosis of FCV infection in cats with conjunctivitis.

Animals↗
PubMed1998

The 42K protein of rice dwarf virus is a post-translational cleavage product of the 46K outer capsid protein.

The outer capsid protein (P8) heterogeneity of rice dwarf virus (RDV) exists not only in purified virus particles, but also in RDV-infected rice, transgenic rice expressing P8, E. coli expression of P8 product and the in vitro translation products of S8. N-terminal amino acid sequencing revealed that P8 is a cleavage product of P8'. The cleavage occurs specifically at the residues of Asp362 and Pro363. The function of the proteolytic processing is unknown.

Capsid↗
PubMed1998

Sequence comparison of the major capsid protein gene from 18 diverse iridoviruses.

Insect iridoviruses (IV) have been found on all continents of the world and in a broad range of insect hosts. The host range for a single strain can cross several insect orders. This along with a paucity of molecular information on all but a few members has led to confusion in the taxonomy and classification of these viruses and in the identification of potentially novel isolates. To address this problem consensus PCR primers were designed to amplify and sequence a 500 bp region of the major capsid protein (MCP) gene. PCR products were amplified from eighteen IVs belonging to the genus Iridovirus. No product was observed for the chloriridovirus IV3. Phylogenetic analysis of the partial MCP gene sequence showed that the iridovirus genus can be divided into three groups. These results support previous studies where a range of molecular techniques were used. Group I contained PjIV and IV31, group II contained IV6 (CIV), IV21, and IV28, and group III contained IV1 (TIV), IV2 (SIV), IV9 (WIV), IV10, IV16, (CzIV), IV18, IV22, IV23 (BbIV), IV24, IV29, IV30, AgIV and an undescribed weevil IV. There was no correlation of relatedness with host of isolation but there was some correlation with geographic region of isolation. Sequence analysis also raised issues concerning the purity of some virus stocks and supported the view that some isolates should be considered as variants of one virus species.

Base Sequence↗
PubMed1999

Major capsid proteins of certain Vibrio and Aeromonas phages are homologous to the equivalent protein, gp23(*), of coliphage T4.

N-terminal amino acid sequences of major capsid proteins (Mcps) of three vibriophages (KVP20, KVP40 and nt-1), two aeromonad phages (Aeh 1 and 65) and coliphage T4 were compared. All these phages are morphologically similar, belonging to family Myoviridae and the vernacular genus name "T4-like phages". A dendrogram constructed from homology data indicated that (i) the three vibriophages were closely related, (ii) the two aeromonad phages were also fairly related and (iii) these five phages were all distantly, but definitely, related to coliphage T4. These results suggest that Mcps of morphologically similar phages are highly conserved and may serve as a measure to assess the phylogenetic relationships among different phages of similar morphology.

Aeromonas↗
PubMed1999

Vibriophage KVP40 and coliphage T4 genomes share a homologous 7-kbp region immediately upstream of the gene encoding the major capsid protein.

Vibriophage KVP40, a large tailed DNA phage morphologically similar to T-even coliphages, has a major capsid protein (Mcp) homologous to the equivalent protein, gp23(*), of coliphage T4. The sequence analysis was extended to a 7-kbp region immediately upstream of the mcp gene encoding the precursor of Mcp. The region as a whole was fairly homologous to the corresponding region of the T4 genome and contained 8 ORFs homologous to T4 genes 17, 18, 19, 20, 67, 68, 21, and 22 in the same order as in T4. These findings thus strongly suggest that these two phages are phylogenetically related.

Amino Acid Sequence↗
PubMed2000

Conformational changes during proteolytic processing of a picornavirus capsid proteins.

We have used synthetic peptide antibodies to probe conformational changes that occur during the cleavage cascade which generates the capsid proteins of a picornavirus. The initial translation product of 97 kDa, the precursor of all four structural proteins, is cleaved to form a 63 kDa fragment which, we show, has significantly different folding characteristics to both its larger parent and its products. We demonstrate that proteolytic cleavages as distant as 520 residues from epitopes confer sufficiently large conformational changes as to render them unrecognisable. To our knowledge, this is the first demonstration of this phenomenon in the picornavirus system.

Animals↗
PubMed2001

Structural dynamics, an intrinsic property of viral capsids.

In this review, we emphasize that high-resolution models of the structures of small plant and animal viruses obtained by X-ray crystallography are static and insufficient to describe the behavior of these virions. Viral capsids are highly flexible and may undergo conformational changes under physiological conditions without collapse of the virions. This flexibility plays a key role in the process of infection.

Animals↗
PubMed2001

Tomato yellow leaf curl virus (TYLCV) capsid protein (CP) subunit interactions: implications for viral assembly.

Tomato yellow leaf curl virus (TYLCV) capsid protein (CP) forms the capsule that encapsidates the viral genomic ssDNA. We have analyzed the homotypic interaction capacity of full-length and mutated CP. We found that full-length CP interacts with itself. Truncation of the protein from the C-terminal led to diminution of the self-interaction process. Also, the N-terminal region of the CP seemed to be necessary for the interaction. As the two deletion mutants interacted successfully with the wildtype protein, while they failed to self-interact, we suggest that the N-terminal amino acids interact with amino acids of the C-terminal region. Changes in CP homotypic interaction capacity were detected when mutations in the middle portion of the protein were introduced.

Blotting, Western↗
PubMed2005

Development of a candidate vaccine for Newcastle disease virus by epitope display in the Cucumber mosaic virus capsid protein.

A peptide fusion to the capsid protein (CP) of Cucumber mosaic virus(CMV) was designed to express either a 17 amino acid (aa) neutralizing epitope of the Newcastle disease virus (NDV) fusion (F) protein or an eight aa neutralizing epitope of the NDV hemagglutinin-neuraminidase (HN) protein. Fusions of the F, HN and HN2 (duplicated HN epitope) were made in the internal betaH-betaI loop (motif 5) within the CMV CP. Recombinant RNA3 transcripts of the Ixora strain of CMV were inoculated on to Nicotiana benthamiana, together with CMV RNA1 and CMV RNA2. When the F and HN epitopes were placed in the internal motif, the modified virus was infectious and the HN NDV epitope was recognized by anti-NDV sera. However, in some plants, deletions of one to several of the inserted amino acids occurred. A duplication of the HN epitope rendered the virus non-viable.

Amino Acid Sequence↗
PubMed2005

Transgenic resistance to Cymbidium mosaic virus in Dendrobium expressing the viral capsid protein gene.

A Taiwan isolate of Cymbidium mosaic virus (CymMV-CS) was isolated from infected Cymbidium sinesis Willd. The cDNA of the capsid protein (CP) gene was synthesized and sequenced. Alignment of this CP gene with other reported CPs revealed homologies of 92-98% at the nucleotide level and 98-99% at the amino acid level. To generate virus-resistant varieties, the CymMV-CS CP gene was transformed into Dendrobium protocorms through particle bombardment. Transformants were selected on medium supplemented with 20 mg/L hygromycin and the presence of the transgene was confirmed by polymerase chain reaction, Southern, Northern and Western blot analyses. Transgenic Dendrobium harboring the CymMV CP gene expressed a very low level of virus accumulation four months post-inoculation with CymMV, as detected by ELISA. The transgenic plants exhibited much milder symptoms than the non-transgenic plants upon challenge with CymMV virions.

Base Sequence↗
PubMed2006

Genetic variability in the sapovirus capsid protein.

Sapovirus (SV), which causes gastroenteritis in humans, is composed of genetically divergent viruses classified into 5 genogroups. In this study, 2.2-kb nucleotide sequences of the 3' terminus of the genome of 15 SV strains detected in Japan were determined. The 15 SV strains could be classified into four genogroups (GI, GII, GIV and GV), and in two of these, GI and GII, 10 genotypes were identified. The amino acid sequences of the central variable region of the capsid protein showed less than 81% identity when strains belonging to different genotypes were compared. It was therefore supposed that antigenic variety exists between different genotypes. These results will be useful for further genetic and antigenic analyses of SV.

Antigenic Variation↗
PubMed2005

The goose reovirus genome segment encoding the minor outer capsid protein, sigma1/sigmaC, is bicistronic and shares structural similarities with its counterpart in Muscovy duck reovirus.

Reoviruses have recently been shown to be associated with disease in young geese and to be involved in epizooties of severe outcome in Hungary. To assess the genetic variability among these pathogenic goose reoviruses (GRVs), we sequenced the S4 genome segment of five GRV strains isolated from different diseased flocks. We found that the GRV S4 genome segment, consisting of two partially overlapping open reading frames (ORFs), shares substantial structural similarity with its counterpart in muscovy duck reoviruses (DRVs). ORF1 is predicted to encode a polypeptide highly similar to the p10 polypeptide of DRV, and ORF2 supposedly encodes the minor outer capsid protein, sigma1/sigmaC. In one of the five GRV strains examined, we identified a single uracil base insertion close to the middle of ORF2. This insertion resulted in a frameshift and in concomitant acquisition of a termination codon (UAA) a few codons downstream, apparently causing truncation of the C-terminal part of the protein. The functional consequences of this assumed mutation, which would result in loss of more than a half of the protein, have yet to be determined. Nonetheless, the sequence and structural similarities between the genome segment encoding sigmal/sigmaC in GRVs and DRVs suggest that these viruses belong to a species distinct from other established species within subgroup 2 of orthoreoviruses.

Amino Acid Sequence↗
PubMed1986

Biosynthesis of reovirus-specified polypeptides. Molecular cDNA cloning and nucleotide sequence of the reovirus serotype 1 Lang strain bicistronic s1 mRNA which encodes the minor capsid polypeptide sigma 1a and the nonstructural polypeptide sigma 1bNS.

Human reovirus serotype 1 Lang strain s1 mRNA, which encodes the minor capsid cell attachment protein sigma 1a and the nonstructural protein sigma 1bNS, was cloned as a cDNA:mRNA heteroduplex in Escherichia coli using phage M13. The Lang strain s1 mRNA is 1462 nucleotides in length and possesses two open reading frames. The first begins at nt 14 and has a coding capacity of 418 amino acids, sufficient to account for sigma 1a; the second begins at nt 75 and has a coding capacity of 119 amino acids, sufficient to account for sigma 1bNS. Comparison of the Lang serotype s1 sequence derived from cDNA clones of s1 mRNA with the Lang S1 sequence derived from cDNA clones of the S1 dsRNA genome segment definitively establishes that reovirus plus-strand mRNA is structurally equivalent to the plus-strand of the dsRNA genome segment.

Base Sequence↗
PubMed1989

Relationship between methylation status and expression of an Epstein-Barr virus (EBV) capsid antigen gene.

The methylation status of the 160 kD viral capsid antigen (VCA) gene promoter was determined by hybridization analysis. The semi-permissive marmoset cell line FF41-1 lacked cytosine methylation in approximately three quarters of the VCA promoter CpG dinucleotide residues. In the stringently infected HH514CL16 cell line the same CpG residues were methylated in three quarters of the genomes. 5'deoxy-5'-S-isobutyladenosine (SIBA), a DNA methylase inhibitor, was utilized to disrupt the EBV latent state. As determined by flow cytometry, SIBA treatment significantly increased expression of VCA. The VCA promoter was hypomethylated in VCA-positive FF41-1 cells sorted by flow cytometry. While hypomethylation alone was not sufficient for VCA transcriptional activity, the absence of methylation of VCA promoter CpG dinucleotide residues was associated with expression of VCA.

Animals↗
PubMed1985

Salt-stable association of simian virus 40 capsid with simian virus 40 DNA.

In 8 M CsCl, a fraction of the wild-type previrions and tsB228 nucleoprotein complexes lose their core histones but retain their capsid. These histone-depleted complexes appear in the electron microscope as a protein shell attached to supercoiled DNA. Consistent with this result, we find that in 1 M NaCl, the wild-type previrions dissociate into two populations of nucleoprotein complexes. One population sediments between 50 and 140 S and morphologically resembles the shell-DNA complexes isolated in CsCl gradients. The other population is comprised primarily of nucleoproteins which sediment at 40 S.

Capsid↗
PubMed1989

A theoretical study of the acidification of the rhinovirus capsid.

Electrostatic calculations for human rhinovirus 14 indicate that histidine-base residue pairs in the region of a beta-strand interaction between pentamers may be involved in a pH-induced process that leads to the release of viral RNA. Other picornavirus sequences are examined for these residue pairs, a subset of which is present in enteroviruses. Foot and mouth disease virus possesses one of the residue pairs, and cardioviruses, which undergo a separate pH and halide ion-induced capsid dissociation, possess none.

Capsid↗
PubMed1996

Spectroscopic study of an HIV-1 capsid protein major homology region peptide analog.

The capsid (CA) domain of retroviral Gag proteins possesses one subdomain, the major homology region (MHR), which is conserved among nearly all avian and mammalian retroviruses. While it is known that the mutagenesis of residues in the MHR will impair virus infectivity, the precise structure and function of the MHR is not known. In order to obtain further information on the MHR, we have examined the structure of a synthetic peptide encompassing the MHR of human immunodeficiency virus type I (HIV-1) CA protein. Multiple sequence alignment and secondary structure prediction indicate that the peptide could form 50% alpha-helix and 10% beta-sheet. In addition, circular dichroism studies indicate that, in the presence of 50% trifluoroethanol (TFE), the peptide adopts an alpha-helical structure over half of its length. Further analysis by proton nuclear magnetic resonance spectroscopy suggests that the C-terminal portion of the MHR forms a helix in aqueous solution. Upon the addition of TFE, the position of the helix remains nearly constant, but the magnitude of the changes in H alpha chemical shifts of the residues indicate a more stable helix. These results suggest that a helical C-terminus of retroviral MHRs may be integral to the function of this region.

Amino Acid Sequence↗

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