PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Viral Structures”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed2002

Poliovirus cell entry: common structural themes in viral cell entry pathways.

Structural studies of polio- and closely related viruses have provided a series of snapshots along their cell entry pathways. Based on the structures and related kinetic, biochemical, and genetic studies, we have proposed a model for the cell entry pathway for polio- and closely related viruses. In this model a maturation cleavage of a capsid protein precursor locks the virus in a metastable state, and the receptor acts like a transition-state catalyst to overcome an energy barrier and release the mature virion from the metastable state. This initiates a series of conformational changes that allow the virus to attach to membranes, form a pore, and finally release its RNA genome into the cytoplasm. This model has striking parallels with emerging models for the maturation and cell entry of more complex enveloped viruses such as influenza virus and HIV.

Capsid↗
PubMed1990

Specific interaction of the human immunodeficiency virus Rev protein with a structured region in the env mRNA.

A region of potential complex secondary structure within the human immunodeficiency virus env mRNA has been implicated in Rev-mediated export of viral structural mRNAs from the nucleus to the cytoplasm. By using an RNase protection gel-mobility-shift assay, we demonstrate that purified Rev protein forms a stable complex with this Rev-responsive RNA. RNAs with mutations designed to disrupt formation of a predicted stem structure no longer interact with Rev. However, Rev binding is restored upon annealing of the two complementary RNAs that make up the stem. These results suggest that direct interaction of Rev with the Rev-responsive element could facilitate transport of human immunodeficiency virus structural mRNAs from the nucleus to the cytoplasm.

Base Sequence↗
PubMed1983

Proteins specified by African Swine Fever virus. IV. Glycoproteins and phosphoproteins.

African Swine Fever virus infected MS cells labeled with radioactive 14C-amino acids, 32Pi or [3H]-glucosamine were examined by high resolution sodium dodecylsulfate polyacrylamide gel electrophoresis and showed 43 infected cell polypeptides. Twenty-one of these proteins were present in the nuclear fraction of infected cells. At least 22 of the infected cell polypeptides induced antibodies during natural infections in swine. The pattern of infected cell polypeptides modified by incorporation of showed prosthetic groups that at least 8 polypeptides were phosphorylated and at least three specific viral glycoproteins (A, B and C) were detected by immunoprecipitation. The most highly glycosylated polypeptide corresponds to the structural viral protein VP51.

African Swine Fever Virus↗
PubMed2005

[Establish a transgenic mice model harboring structural genes of hepatitis C virus].

OBJECTIVES: To establish an animal model of HCV transgenic mice to elucidate the pathogenesis of hepatitis C virus infection and function of the viral structural proteins. METHODS: Structural gene of HCV were amplified and recombined into eukaryotic expression vectors, pcDNA4HisMax and pMT/BiP/V5-His A, after their expressive activity was confirmed to detect the structural protein in the transfected COS7 and S2 cells by Western blot. The fertilized expression element, which contained CMV or pMT promoter, structural gene of HCV and polyadenylation signal sequence, was microinjected into 1736 C57BL/6 mouse fertilized ova. The ova were then replanted into the oviducts of 69 pseudopregnant recipient mice. RESULTS: Twenty-five recipient mice were impregnated and later produced 105 newborns; 49 of them died from unknown causes and 57 survived. After the specific HCV structural genes were identified by PCR and Southern blot hybridization, 26 founders were obtained; among them 10 were stable expression mice and 16 were the inducible ones. The rate of founders developed from implanted embryos was only 1.50%. Through hybridization with normal mice, 58 hybrid mice have been obtained at present. CONCLUSION: Two kinds of different transgenic mice of HCV were developed; one is of stable expression, and the other is inducible. This transgenic mice model may create an opportunity for studying the function of the structural gene of HCV and elucidate its pathogenicity.

Animals↗
PubMed1993

Immunological cross-reactions and interactions between the Drosophila melanogaster ref(2)P protein and sigma rhabdovirus proteins.

The ref(2)P gene is one of the Drosophila melanogaster genes involved in the inhibition of sigma rhabdovirus multiplication. The partial restriction of viral replication varies according to the ref(2)P alleles and virus strains and involves intracellular interactions between parasite and host products. We identified the protein encoded by the ref(2)P gene and produced polyclonal antibodies directed against the whole ref(2)P protein obtained from a recombinant baculovirus and against a part of the protein expressed as a fusion protein. These antibodies were used to study the interactions with sigma virus proteins by different immunoprecipitation techniques. We showed that the native ref(2)P protein shared conformation-dependent common epitopes with the viral structural genome-associated N protein. Furthermore, the cellular protein was found to be associated in complexes with the viral P protein required for RNA polymerase activity. The significance of these observations in the control of sigma virus multiplication by its host is discussed.

Animals↗
PubMedDate not supplied

Characterization of viral polypeptides from avian rotavirus.

The synthesis of avian rotavirus (AvRV-1) polypeptides in MA 104 cells was investigated. Extracts of cells labeled with either [35S]methionine or [3H]mannose were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Viral protein synthesis was detected first at 6 hours postinfection. Ten major viral polypeptides were detected at this time. The presence of five viral structural proteins (100K, 90K, 88K, 45K, and 37K) were demonstrated in AvRV-1-infected cells by immunoprecipitation analysis. One structural polypeptide (37K) was identified as a glycoprotein. Two viral polypeptides (30K and 28K) were identified as nonstructural glycoproteins. By tunicamycin inhibition of glycosylation, a 32K polypeptide was identified. This 32K polypeptide later was proven to be the precursor of 37K structural glycoprotein by immunoprecipitation analysis, beta-N-acetylglucosaminidase H (Endo H) treatment, and peptide mapping analysis. Avian rotavirus contained high-mannose oligosaccharide content in the glycoproteins similar to the glycoproteins of mammalian rotaviruses.

Animals↗
PubMed2005

Infectious bursal disease virus recovery from Vero cells transfected with RNA transcripts is enhanced by expression of the structural proteins in trans.

Positive sense RNA transcripts of infectious bursal disease (IBD) virus genome segments A and B have previously been shown to be infectious. In this study we demonstrate that recovery of IBD virus from the transfection of Vero cells with positive sense RNA transcripts of genome segments A and B was enhanced by expression of the viral structural proteins VP2 with VP3 or by expression of viral polyprotein VP243 from DNA plasmids in trans. Expression of individual viral proteins VP2, VP3, or VP4 alone from DNA plasmids did not enhance IBD virus recovery. Earliest virus recovery from transfection of positive sense RNA transcripts of genomic segments A and B was at 36 h and mean titers were 10(1.8) pfu/ml. IBD virus was recovered 6 hours after transfection in cells concurrently expressing either VP2 with VP3 or VP243 and mean titers were 10(8.5) pfu/ml or 10(9.2) pfu/ml, respectively. Likewise, expression of the viral polyprotein from DNA plasmid increased the permissiveness of Vero cells for infection with non-culture adapted IBD virus. The titer of recovered non-culture adapted virus from 10(3.3) pfu/ml to 10(10.3) pfu/ml with expression of the viral polyprotein. This report is the first to describe a reverse genetics model for IBD virus with high efficiency of virus recovery for non-culture adapted strains.

Animals↗
PubMed1997

A single amino acid change in the E2 glycoprotein of Sindbis virus confers neurovirulence by altering an early step of virus replication.

Amino acid changes in the envelope glycoproteins of Sindbis virus have been linked to neurovirulence; however, the molecular mechanisms by which these amino acid changes alter neurovirulence are not known. Recombinant-virus studies have mapped an important determinant of neurovirulence in adult mice to a single amino acid change, glutamine to histidine, at position 55 of the E2 glycoprotein (P. C. Tucker, E. G. Strauss, R. J. Kuhn, J. H. Strauss, and D. E. Griffin, J. Virol. 67:4605-4610, 1993). To investigate how histidine confers neurovirulence, we examined the various stages of the virus life cycle in neural (N18) and nonneural (BHK) cells. In BHK cells, recombinant viruses 633 (E255Q) and TE (E255H) replicated similarly. In contrast, in N18 neuroblastoma cells, TE established infection more efficiently, replicated faster, and achieved higher rates of virus release than did 633. Viral structural protein synthesis was similar in 633- and TE-infected BHK cells, while in N18 cells, structural protein synthesis was detected only in TE-infected cells at 6 h and remained higher for at least 16 h postinfection. Viral RNA synthesis was initiated more rapidly and was up to fivefold greater in TE- versus 633-infected N18 cells. Taken together with other data demonstrating minimal effects on virus binding and entry (P. C. Tucker, S. H. Lee, N. Bui, D. Martinie, and D. E. Griffin, J. Virol. 71:6106-6112, 1997), these data suggest that E2 position 55 plays an important role at early stages of infection of neural cells, thereby facilitating neurovirulence.

Animals↗
PubMed1973

In vitro protein-synthesizing activity of vesicular stomatitis virus-infected cell extracts.

Crude cytoplasmic extracts from vesicular stomatitis virus (VSV)-infected HeLa cells incorporate radioactive amino acids into hot trichloroacetic acid-precipitable material linearly for 10 to 20 min. The material synthesized in vitro corresponds in molecular weight to four of the five VSV structural proteins. However, synthesis of the viral glycoprotein (G) is significantly reduced, whereas the relative amounts of viral structural proteins L and NS synthesized are increased compared with the ratio of the proteins found in the virion. Fractionation of a VSV-infected crude cytoplasmic extract into a cytoplasmic pellet (20,000 x g for 30 min) and a cytoplasmic supernatant results in a significant reduction in protein synthesizing activity of both fractions, although both contain polysomes. The products synthesized by a cytoplasmic supernatant-directed system included all the VSV structural proteins except the glycoprotein, whereas in an in vitro system directed by the cytoplasmic pellet there is a marked reduction in synthesis of the nucleoprotein (N) and also a small relative increase in synthesis of the glycoprotein. Addition of uninfected, preincubated HeLa or L-cell S10 or a HeLa ribosomal fraction to the VSV-infected cytoplasmic pellet results in a 30- to 60-fold stimulation of (35)S-methionine incorporation. However, these uninfected extracts do not stimulate (35)S-methionine incorporation by the infected crude cytoplasmic extract or the cytoplasmic supernatant. The products synthesized by the stimulated cytoplasmic pellet now include sizeable amounts of the glycoprotein in addition to the other VSV structural proteins.

Amino Acids↗
PubMed1999

Purification and characterization of the assembly factor P17 of the lipid-containing bacteriophage PRD1.

Assembly factors, proteins assisting the formation of viral structures, have been found in many viral systems. The gene encoding the assembly factor P17 of bacteriophage PRD1 has been cloned and expressed in Escherichia coli. P17 acts late in phage assembly, after capsid protein folding and multimerization, and sorting of membrane proteins has occurred. P17 has been purified to near homogeneity. It is a tetrameric protein displaying a rather high heat stability. The protein is largely in an alpha-helical conformation and possesses a putative leucine zipper which is not essential for protein function, as judged by in vitro mutagenesis and complementation analysis. Although heating does not cause structural changes in the conformation of the protein, the dissociation of the tetramer into smaller units is evident as diminished self-quenching of the fluorescently labeled P17. Similarly, dissociation of the tetramer is also obtained by dialysis of the protein against 6-M guanidine hydrochloride (GdnHCl) or 1% SDS. The reassembly of these smaller units upon cooling is evident from resonance energy transfer.

Bacteriophages↗
PubMed1999

Ribosomal protein L3 mutants alter translational fidelity and promote rapid loss of the yeast killer virus.

Programmed -1 ribosomal frameshifting is utilized by a number of RNA viruses as a means of ensuring the correct ratio of viral structural to enzymatic proteins available for viral particle assembly. Altering frameshifting efficiencies upsets this ratio, interfering with virus propagation. We have previously demonstrated that compounds that alter the kinetics of the peptidyl-transfer reaction affect programmed -1 ribosomal frameshift efficiencies and interfere with viral propagation in yeast. Here, the use of a genetic approach lends further support to the hypothesis that alterations affecting the ribosome's peptidyltransferase activity lead to changes in frameshifting efficiency and virus loss. Mutations in the RPL3 gene, which encodes a ribosomal protein located at the peptidyltransferase center, promote approximately three- to fourfold increases in programmed -1 ribosomal frameshift efficiencies and loss of the M1 killer virus of yeast. The mak8-1 allele of RPL3 contains two adjacent missense mutations which are predicted to structurally alter the Mak8-1p. Furthermore, a second allele that encodes the N-terminal 100 amino acids of L3 (called L3Delta) exerts a trans-dominant effect on programmed -1 ribosomal frameshifting and killer virus maintenance. Taken together, these results support the hypothesis that alterations in the peptidyltransferase center affect programmed -1 ribosomal frameshifting.

Alleles↗
PubMed1989

Comparison of immune response to rubella virus proteins in early and late natural infections.

The immunological response to rubella virus structural proteins was analyzed by immunoprecipitation assay in sera collected in Cordoba, Argentina, during early convalescence and after remote natural infections. All of the viral structural proteins, the two glycoproteins E1 and E2, and the nucleocapsid C protein, were precipitated by sera obtained from patients soon after infection. By contrast, C reactive antibodies were not detected in sera from remote infections. These results suggest that E1 and E2 play a major role in the long-lasting protective immunity to rubella virus.

Adult↗
PubMed1992

Effective vaccination against papilloma development by immunization with L1 or L2 structural protein of cottontail rabbit papillomavirus.

Immunization of rabbits with either L1, the major structural protein, or L2, a minor structural protein of cottontail rabbit papillomavirus (CRPV), protected against challenge with the virus. Neutralizing antibodies were elicited by both the L1 and L2 trpE fusion proteins. Neutralization with anti-L1 serum, however, was more efficient than with anti-L2 serum. In contrast, when tested on Western blots the immune response to L2 was stronger than to L1. Rabbits were also protected against CRPV infection by immunization with L1 expressing recombinant vaccinia virus. Sera from two of three rabbits immunized with recombinant vaccinia virus were negative on Western blots but all three were positive in ELISA's with nondenatured fusion protein or in immunoprecipitations. The results suggest that both the viral structural proteins, L1 and L2, merit consideration in the development of a vaccine against papillomavirus.

Animals↗
PubMed1980

Field-flow fractionation of alkali-liberated nuclear polyhedrosis virus from gypsy moth Lymantria dispar Linnaeus.

Rod-shaped viral particles of the gypsy moth nuclear polyhedrosis virus (NPV) were obtained through alkaline dissolution of inclusion bodies isolated and purified from infected hosts. The liberated viral fraction contains a wide assortment of enveloped aggregated forms as well as enveloped monomers. This complex mixture was separated by means of sedimentation field-flow fractionation (sedimentation FFF) to give a mass spectrum of the separated particles. From the elution pattern effective molecular weights could be assigned to the various resolved components. Through electron microscopy it was possible to characterize the components as monomers, dimers, etc. In parallel experiments the same viral mixture was separated by the more commonly used density gradient sedimentation technique. The two methods are compared as to time and convenience of manipulation, as well as to the amount of physicochemical information that can be extracted from each separation. The mixture of aggregate viral structures was dialyzed against a nonionic detergent solution. Sedimentation FFF of the dialysate revealed a uniform population of non-enveloped particles with no effective molecular weight which was lower than that of the initial monomer fraction. Electron microscopic observations confirmed that this lower molecular weight fraction did indeed contain rod-like structures which were thinner than the initial enveloped monomers indicating that most if not all of the enveloped material had been removed from the viral rod structures.

Animals↗
PubMed1974

Murine sarcoma virus gene expression: transformants which express viral envelope glycoprotein in the absence of the major internal protein and infectious particles.

Expression of the major internal protein and the envelope glycoprotein of murine C-type viruses in focus-derived lines of normal rat kidney cells infected with Kirsten murine sarcoma virus was measured by radioimmunoassay. Of the clones selected, which do not produce virus particles or the major viral structural protein, approximately half express the viral envelope glycoprotein at concentrations found in productively infected cells. Expression of the envelope glycoprotein did not appear to alter significantly the properties of the transformed cells in culture.

Animals↗
PubMed2006

Supramolecular architecture of severe acute respiratory syndrome coronavirus revealed by electron cryomicroscopy.

Coronavirus particles are enveloped and pleomorphic and are thus refractory to crystallization and symmetry-assisted reconstruction. A novel methodology of single-particle image analysis was applied to selected virus features to obtain a detailed model of the oligomeric state and spatial relationships among viral structural proteins. Two-dimensional images of the S, M, and N structural proteins of severe acute respiratory syndrome coronavirus and two other coronaviruses were refined to a resolution of approximately 4 nm. Proteins near the viral membrane were arranged in overlapping lattices surrounding a disordered core. Trimeric glycoprotein spikes were in register with four underlying ribonucleoprotein densities. However, the spikes were dispensable for ribonucleoprotein lattice formation. The ribonucleoprotein particles displayed coiled shapes when released from the viral membrane. Our results contribute to the understanding of the assembly pathway used by coronaviruses and other pleomorphic viruses and provide the first detailed view of coronavirus ultrastructure.

Cryoelectron Microscopy↗
PubMed1992

Phosphorylation regulates RNA binding by the human T-cell leukemia virus Rex protein.

The Rex protein of human T-cell leukemia virus types I (HTLV-I) and II (HTLV-II) regulates the expression of the viral structural genes and is critical for viral replication. Rex acts by specifically binding to RNAs containing sequences of the R region of the 5' long terminal repeat. Two forms of Rex detected in HTLV-II-infected cells, p26rex and p24rex, differ in the extent of serine phosphorylation. Two-dimensional phosphopeptide analysis indicates that p26rex is extensively phosphorylated at multiple sites. Using a sensitive immunobinding assay, we show that the phosphorylation state of Rex determines the efficiency of binding of Rex to HTLV-II target RNAs. Thus, the phosphorylation state of Rex in the infected cell may be a switch that determines whether virus exists in a latent or productive state. These studies also suggest that phosphorylation of RNA-binding regulatory proteins is a more general mechanism of gene regulation.

Baculoviridae↗