Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Capsid”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,063 records · Page 59Linked to original sources
PubMed1981

Modification of the poliovirus capsid by ultraviolet light.

Ultraviolet (UV) irradiation of type I poliovirus resulted in a modified (M) particle that had lost infectivity, lacked ability to adsorb to HeLa cells, lacked VP4, and reduced in S value. Additional irradiation resulted in the loss of VP2, further reduction in S value, and permeability of the capsid to RNAse, This particle (C) as well as M contain the genome. Acid pH (5.5-65) and sulfhydryl-reducing substances (dithiothreitol. reduced glutathione, and L-cysteine) inhibited UV-induced modification of the capsid. UV irradiation at alkaline pH (7.5-8.5) resulted in more extensive modification of the capsid than irradiation at neutral pH. Ionic compounds were found to inhibit the modifying reaction.

Adsorption↗
PubMed2002

RNA bacteriophage capsid-mediated drug delivery and epitope presentation.

OBJECTIVE: To use our knowledge of the three-dimensional structure and self-assembly mechanism of RNA bacteriophage capsids to develop novel virus-like particles (VLPs) for drug delivery and epitope presentation. METHODS: Site-directed mutagenesis of a recombinant MS2 coat protein expression construct has been used to generate translational fusions encompassing short epitope sequences. These chimeric proteins still self-assemble in vivo into T = 3 shells with the foreign epitope in an accessible location. Covalent conjugation has also been used to generate RNA stem-loops attached to the toxin, ricin A chain, or to nucleotide-based drugs, that are still capable of stimulating self-assembly of the capsid in vitro. These packaged drugs can then be directed to specific cells in culture by further covalent decoration of the capsids with targeting molecules. RESULTS: Chimeric VLPs are strongly immunogenic when carrying either B or T cell epitopes, the latter generating cytokine profiles consistent with memory responses. Immune responses to the underlying phage epitopes appear to be proportional to the area of the phage surface accessible. Phage shells effectively protect nucleic acid-based drugs and, for the toxin construct, make cell-specific delivery systems with LD50 values in culture sub-nanomolar. CONCLUSION: VLP technology has potential for therapeutic and prophylactic intervention in disease.

Amino Acid Sequence↗
PubMed1990

Bovine serological response to a recombinant BPV-1 major capsid protein vaccine.

Four of five groups of Holestine by Angus calves (5 calves/group) were immunized with different formulations of a recombinant BPV-1 DNA vaccine using a BPV-1 major capsid:B-galactosidase fusion protein as the immunogen. Group 5 was not vaccinated. Vaccinated calves received the vaccine on days 0 and 21 of the trial, and calves from all five groups were challenged intradermally with 10(10) BPV-1 particles at each of two different sites on day 56. All calves were bled on days 3, 24, 55, 77, and 104 of the trial, and the sera were tested for reactivity with intact and disrupted BPV-1 particles by ELISA. At the time of challenge with BPV-1 virions (day 56), 19 of 20 vaccinated calves were seropositive for disrupted BPV-1 particles; sera from 3 of 20 calves reacted with intact BPV-1 virions. By day 77, 11 of 19 vaccinated calves had developed antibody titers to intact BPV-1 virions; only 1 calf in group 5 developed antibodies (transiently) against BPV-1 capsid epitopes. After challenge, 24 of 25 calves from the five groups developed intradermal fibromas, the biological end point of this study. Fibromas appeared to increase in size in group 5 (unvaccinated, inoculated controls), whereas most tumors from the four vaccinated groups (1-4) stabilized or decreased in size. Although the calves developed fibromas, 90% of calves (in groups 1-4) developed antibodies against disrupted BPV-1 capsid proteins whereas 58% developed antibodies that reacted with intact virions. The immunologic response of vaccinated calves to intact and disrupted BPV-1 particles appeared to be determined in large part by the various formulations of the vaccine, particularly the adjuvant.

Animals↗
PubMed1993

Identification of conformational epitopes of the BPV-1 capsid recognized by competitive inhibition of sera from infected or immunized animals.

Conformational papillomavirus (PV) capsid epitopes are the major targets of neutralizing antibodies. BPV1 virion surface epitopes were analyzed for type-specificity, induction of neutralization, and topographical location with antibodies from selected humans, and BPV1 or -2 immunized or infected cattle, rabbits and mice. Rabbit sera produced against deer PV (DPV) or BPV2 and human sera reacted with intact BPV1 in ELISA, indicating the presence of cross-reactive conformational epitopes on the surface of BPV1 virions. However, competitive binding assays performed on intact BPV1 capsids using unlabeled and biotin-conjugated antibodies revealed that the conformational epitopes of BPV1 recognized by rabbit, bovine and human antibodies were topographically different. Only hyperimmune sera to intact BPV1, BPV2 or DPV neutralized BPV1-induced focus formation of C127 cells with the highest neutralizing titers observed for bovine and rabbit antibodies produced against intact BPV1. Our study showed the complexity of conformational capsid epitopes of BPV1 and their importance for inducing a protective humoral immune response in animals inoculated or immunized with BPV1.

Antibodies, Viral↗
PubMed2006

Characterization of neutralizing epitopes within the major capsid protein of human papillomavirus type 33.

BACKGROUND: Infections with papillomaviruses induce type-specific immune responses, mainly directed against the major capsid protein, L1. Based on the propensity of the L1 protein to self-assemble into virus-like particles (VLPs), type-specific vaccines have already been developed. In order to generate vaccines that target a broader spectrum of HPV types, extended knowledge of neutralizing epitopes is required. Despite the association of human papillomavirus type 33 (HPV33) with cervical carcinomas, fine mapping of neutralizing conformational epitopes on HPV33 has not been reported yet. By loop swapping between HPV33 and HPV16 capsid proteins, we have identified amino acid sequences critical for the binding of conformation-dependent type-specific neutralizing antibodies to surface-exposed hyper variable loops of HPV33 capsid protein L1. RESULTS: Reactivities of monoclonal antibodies (mAbs) H33.B6, H33.E12, H33.J3 and H16.56E with HPV16:33 and HPV33:16 hybrid L1 VLPs revealed the complex structures of their conformational epitopes as well as the major residues contributing to their binding sites. Whereas the epitope of mAb H33.J3 was determined by amino acids (aa) 51-58 in the BC loop of HPV33 L1, sequences of at least two hyper variable loops, DE (aa 132-140) and FGb (aa 282-291), were found to be essential for binding of H33.B6. The epitope of H33.E12 was even more complex, requiring sequences of the FGa loop (aa 260-270), in addition to loops DE and FGb. CONCLUSION: These data demonstrate that neutralizing epitopes in HPV33 L1 are mainly located on the tip of the capsomere and that several hyper variable loops contribute to form these conformational epitopes. Knowledge of the antigenic structure of HPV is crucial for designing hybrid particles as a basis for intertypic HPV vaccines.

Antibodies, Viral↗
PubMed2007

Interaction between Bluetongue virus outer capsid protein VP2 and vimentin is necessary for virus egress.

BACKGROUND: The VP2 outer capsid protein Bluetongue Virus (BTV) is responsible for receptor binding, haemagglutination and eliciting host-specific immunity. However, the assembly of this outer capsid protein on the transcriptionally active viral core would block transcription of the virus. Thus assembly of the outer capsid on the core particle must be a tightly controlled process during virus maturation. Earlier studies have detected mature virus particles associated with intermediate filaments in virus infected cells but the viral determinant for this association and the effect of disrupting intermediate filaments on virus assembly and release are unknown. RESULTS: In this study it is demonstrated that BTV VP2 associates with vimentin in both virus infected cells and in the absence of other viral proteins. Further, the determinants of vimentin localisation are mapped to the N-terminus of the protein and deletions of amino acids between residues 65 and 114 are shown to disrupt VP2-vimentin association. Site directed mutation also reveals that amino acid residues Gly 70 and Val 72 are important in the VP2-vimentin association. Mutation of these amino acids resulted in a soluble VP2 capable of forming trimeric structures similar to unmodified protein that no longer associated with vimentin. Furthermore, pharmacological disruption of intermediate filaments, either directly or indirectly through the disruption of the microtubule network, inhibited virus release from BTV infected cells. CONCLUSION: The principal findings of the research are that the association of mature BTV particles with intermediate filaments are driven by the interaction of VP2 with vimentin and that this interaction contributes to virus egress. Furthermore, i) the N-terminal 118 amino acids of VP2 are sufficient to confer vimentin interaction. ii) Deletion of amino acids 65-114 or mutation of amino acids 70-72 to DVD abrogates vimentin association. iii) Finally, disruption of vimentin structures results in an increase in cell associated BTV and a reduction in the amount of released virus from infected cells.

Acrylamide↗
PubMed2004

Measurements of DNA lengths remaining in a viral capsid after osmotically suppressed partial ejection.

The effect of external osmotic pressure on the extent of DNA ejection from bacteriophage-lambda was recently investigated (Evilevitch et al., 2003). The total length of DNA ejected was measured via the 260-nm absorption by free nucleotides, after opening of the capsids in the presence of varying amounts of polyethylene glycol 8000 and DNase I. As a function of osmolyte concentration, this absorption was shown to decrease progressively, ultimately vanishing completely for a sufficiently high external osmotic pressure. In this work we report the results of both sedimentation and gel analysis of the length of DNA remaining inside the capsids, as a function of osmolyte concentration. It is confirmed in this way that the progressive inhibition of DNA ejection corresponds to partial ejection from all of the capsids.

Absorption↗
PubMed2000

Nuclear import and DNA binding of human papillomavirus type 45 L1 capsid protein.

During the life cycle of human papillomaviruses (HPVs), the L1 capsid proteins seem to enter the nucleus twice: once after the virions infect the cells, and later during the productive phase when they assemble the replicated HPV genomic DNA into infectious virions. We established for the high-risk HPV45 that when digitonin-permeabilized HeLa cells were incubated with L1 homopentameric capsomers, the HPV45 L1 protein was imported into the nucleus in a receptor-mediated manner. In contrast, intact capsids were not able to enter the nucleus. Immunoisolation assays showed that HPV45 L1 capsomers interact with cytosolic karyopherin alpha 2 beta 1 heterodimers. HPV45 L1 bound strongly to karyopherin alpha 2, and weakly to karyopherin beta 1, as did its nuclear localization signal (NLS). Nuclear import of HPV45 L1, or of a GST-NLS(HPV45L1) fusion protein was efficiently mediated by karyopherin alpha 2 beta 1 heterodimers, and only weakly by karyopherin beta 1. Nuclear import required RanGDP, but was independent of GTP hydrolysis by Ran. Together, these data suggest that the major nuclear import pathway for HPV45 L1 major capsid protein in infected host cells is mediated by karyopherin alpha 2 beta 1 heterodimers and that GTP hydrolysis by Ran is not required for import. Remarkably, HPV45 L1 capsomers can interact nonspecifically with different types of HPV-DNA, and the DNA binding region of HPV45 L1 overlaps with its NLS sequence.

Amino Acid Sequence↗
PubMed2000

Highly conserved nucleotide sequence and its deduced amino acids of the 5'-noncoding region and the capsid protein of a Bangkok isolate dengue-3 virus.

The dengue-3 virus genome encodes an uninterrupted open reading frame (ORF) flanked by 5' and 3' non-coding regions. The order of proteins encoded in dengue-3 virus ORF, as with other flaviviruses, is: Cap 5'-C-prM-E-NS1-NS2A-NS2B-NS3-NS4A-NS4B-NS5-3'. The nucleotide sequence of the 5'-noncoding region and the capsid protein of dengue-3virus (a Bangkok isolate: CH53489 isolated by USAMC-AFRIMS in 1973) has been analyzed in both forward and reverse directions. The PCR-based cycle sequencing technique by the enzymatic method of Sanger et al (1977) using a sequencing primer 5'-end labeled with gamma32P-ATP is the method of our choice for sequencing analysis. One cDNA template was prepared by RT-PCR technique starting from the 5'-end nucleotide 1-465 of the dengue-3 genome. In our cycle sequencing experiments, the substitution of 7-deaza-dG was used for dG in DNA eliminated much of the secondary structures that produced gel artifacts. The final sequence result of this cDNA template was established from its sequence data determined on both strands in opposite directions. Alignment between the newly established nucleotide sequence as well as its deduced amino acid sequence of the Bangkok dengue-3 virus and the published sequence data of the dengue-3 prototype (H87) was manipulated by the PC-DOS-GIBIO-DNASIS TM 06-00 (Hitachi Software). According to the deduced amino acid sequence of the Bangkok dengue-3 virus, its C protein was found to be highly positively charged because of large numbers of lysine and arginine. The homology of the nucleotide sequence between the two dengue-3 virus revealed 97%. The deduced amino acid sequences from the nucleotides 95-465 of the two viruses showed the same indicating highly conserved capsid proteins. Multiple alignment of the nucleotide sequences as well as the deduced amino acid sequences among the Bangkok dengue-3 virus and other dengue 3 viruses also confirmed the highly conserved 5'-noncoding regions and the capsid proteins.

Amino Acid Sequence↗
PubMed1993

Identification of amino acid sequences in the polyomavirus capsid proteins that serve as nuclear localization signals.

The molecular mechanism participating in the transport of newly synthesized proteins from the cytoplasm to the nucleus in mammalian cells is poorly understood. Recently, the nuclear localization signal sequences (NLS) of many nuclear proteins have been identified, and most have been found to be composed of a highly basic amino acid stretch. A genetic "subtractive" and a biochemical "additive" approach were used in our studies to identify the NLS's of the polyomavirus structural capsid proteins. An NLS was identified at the N-terminus (Ala1-Pro-Lys-Arg-Lys-Ser-Gly-Val-Ser-Lys-Cys11) of the major capsid protein VP1 and at the C-terminus (Glu307 -Glu-Asp-Gly-Pro-Glu-Lys-Lys-Lys-Arg-Arg-Leu318) of the VP2/VP3 minor capsid proteins.

Amino Acid Sequence↗
PubMed1991

Use of liposomes, viral capsids, and nanoparticles as DNA carriers.

We tested a variety of liposomes for parameters such as DNA binding capacity and DNase I protection of incorporated and attached DNA to elucidate their use as vehicles for DNA transfer into cells and animals. The results were compared to other potential DNA vehicles, empty viral capsids, and nanoparticles. Maximal binding capacity was achieved for positively charged nanoparticles, DNase I protection was observed for most preparations with neosome preparations being least efficient. The uptake of radiolabeled DNA by cells in culture was determined for cationic and nonionic surfactant vesicles, viral capsids, and nanoparticles. Cellular DNA uptake was best for dioleoyl-derived positively charged liposomes (N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride; DOTMA) and the DNA could be shown to be physiologically active. The recombination rate for DNA fragments transfected in polyoma capsids in live mice was higher than for liposome mediated transfection. Homologous recombination could be observed for both DOTMA and polyoma-mediated DNA transfer.

Animals↗
PubMed1989

Characterization of bacteriophage P22 tailspike mutant proteins with altered endorhamnosidase and capsid assembly activities.

The tailspike protein of Salmonella typhimurium phage P22 is a multifunctional homotrimer which is involved in the terminal reaction of phage assembly, the adsorption of the phage to susceptible cells, and the hydrolysis of the Salmonella O-antigen during the first steps of phage infection. The proteins made from 15 mutant tailspike structural genes carried on high level expression plasmids have been analyzed with respect to their in vivo stability, quaternary structure, capsid assembly activity, and enzymatic activity. Nine mutants synthesize tailspike proteins which fail to accumulate to any appreciable level in vivo, and thus these proteins are probably degraded. Four other altered proteins accumulate in vivo as soluble monomers. The remaining two altered proteins accumulate in vivo as stable trimers. Each of these two proteins is defective for at least one of the known functions of the tailspike protein. One is defective in the capsid assembly reaction and shows an unusual quaternary structural defect but is normal with respect to the enzymatic hydrolysis of O-antigen. The other is defective in the enzymatic hydrolysis of O-antigen but is normal with respect to its capsid assembly activity and quaternary structure. The known sequence changes which give rise to these altered proteins and those of previously identified mutants allow the description of possible functional and structural "domains" of this multifunctional protein.

Capsid↗
PubMed1988

Computer emulation of thin section electron microscopy predicts an envelope-associated icosadeltahedral capsid for human immunodeficiency virus.

Electron microscopy of human immunodeficiency virus (HIV) has provided evidence for a virion model which when sectioned, consists of a circular envelope surrounding an inner conical core. When sections are perpendicular to the core axis, the envelope is still circular, but the tapered core appears as a dot near the center of the envelope. An observation inconsistent with the present model is the frequent finding of an electron-lucent "polygonal window" associated with the virion envelope. Here, we provide evidence for a new model of HIV. This model, which accounts for the polygonal windows and the shape of the envelope, places the conical core inside a regular polyhedron that lies just under the envelope. We tested the validity of various polyhedrons with three-dimensional computer graphics which emulate thin section electron microscopy. With this technique, about 2000 computer-generated "thin sections" of HIV-models were compared with electron micrographs of HIV. A structure consistent with the computer-generated data reveals a detailed model for HIV with the following features; (a) the conical core is inside an envelope-associated capsid having icosadeltahedral symmetry. This envelope-associated capsid is 60-sided and contains 32 vertices, 20 of which have hexagonal symmetry and 12 of which have pentagonal symmetry, (b) the inner rodlike core abuts the inside of any 2 opposing hexagonal vertices, (c) the pentagonal vertices do not support the inner core. A comparison of these results with that of Gelderblom et al. (Gelderblom HR, Hausmann EHS, Ozel M, Pauli G, Koch MA: Fine structure of HIV and immunolocalization of structural proteins. Virology 156: 171, 1987), suggests that the p17 polypeptide is a component of the envelope-associated icosadeltahedral capsid. This computer emulation technique provides a thorough test of this model of HIV, but does not constitute proof. Additional testing methods such as bidirectional metal shadowing and freeze etching will be needed to confirm this new virion structure. Additionally, this computer technique may be useful for testing the proposed morphology for cell organelles.

Capsid↗
PubMed1988

Translational regulation of B19 parvovirus capsid protein production by multiple upstream AUG triplets.

The B19 parvovirus produces two capsid proteins in strikingly different quantities (VP1 less than 4%, VP2 greater than 96%) from overlapping RNAs that are derived from the same transcription unit. Immediately upstream from the VP1 translation initiation site is an unusual sequence containing multiple ATG triplets. During RNA processing this sequence is spliced out of VP2 RNA. To test the regulatory role on translation of this sequence containing upstream AUGs, synthetic RNAs were produced in vitro by T7 RNA polymerase from various plasmid constructions. Translation of VP1 RNA was very inefficient compared to VP2 RNA in a cell-free system, indicating that capsid protein production was regulated at the level of translation. Removal of upstream AUG sequences from VP1 RNA greatly increased the efficiency of translation. Conversely, the addition of the same AUG-rich sequence upstream of the initiation site of VP2 decreased its translation. These data indicate that an upstream AUG-rich region acts as a negative regulatory element in the translational control of B19 capsid protein production.

Capsid↗
PubMed1978

Proteolysis of the major capsid protein T4 bacteriophage polyheads limited by quaternary structure.

Bacteriophage T4 carrying an amber mutation in gene 22 plus an amber mutation in gene 21 form aberrant, tubular structures termed rough polyheads, instead of complete phage when they infect Escherichia coli B. These rough polyheads consist almost entirely of the major capsid protein in its uncleaved form (gp23). When rough polyheads are treated under mild conditions with any of the five proteases, trypsin, chymotrypsin, thermolysin, pronase, or the protease from Staphylococcus aureus V8, the gp23 is rapidly hydrolyzed at a limited number of peptide bonds. In contrast, cleaved capsid protein (gp23) in mature phage capsids is completely resistant to proteolysis under the same conditions. A major project in this laboratory requires determining the primary structure of gp23, a large protein (Mr = 58,000) quite rich in those amino acids at which cleavages are achieved by conventional means. Recovery of peptides from the complex mixtures resulting from such cleavages proved to be extremely difficult. The limited proteolysis of gp23 in rough polyheads had yielded a set of large, easily purified fragments which are greatly simplifying the task of determining the primary structure of this protein.

Amino Acid Sequence↗
PubMed1982

Polyoma-like particle: characterization of the DNA encapsidated in vitro by polyoma empty capsids.

Polyoma empty capsids and DNA interact in a cell-free system to form a polyoma-like particle (PLP). The particle is stable in high concentrations of salt and contains a DNA fragment that is protected by the capsid from the action of DNase I. The DNA extracted from PLP is heterogeneous in size. It has a mean molecular weight of 1.2 x 10(6) with a standard deviation of +/- 0.5 x 10(6). Analysis of PLP DNA with restriction endonucleases and the Southern blot technique reveals that a specific primary sequence is not required for PLP formation. Either linear, circular, or supercoiled polyoma DNA, as well as single-stranded DNA, rRNA, and the synthetic homopolymers poly(dA) . poly(dT) and poly(dG) . poly(dC) can be used for PLP formation. It is concluded that polyoma empty capsids can be used to bind and encapsidate nucleic acids differing in their primary, secondary, and superhelical tertiary structure to form, in vitro, stable polyoma-like particles.

Capsid↗
PubMed1983

Arrangement of hexons and polypeptide subunits in the adenovirus capsid.

With direct analysis of electron micrographs and with Markham's rotational integration technique we have demonstrated that in the adenovirus capsid the triangular profile of the hexon-end facing are formed by one polypeptide each and the sides by two neighbouring polypeptides. The mutual rotational and spatial orientation of the three hexon polypeptide subunits has been determined in relation to each other and to the pentons. Two polypeptides of the peripentonal hexons are oriented towards the penton. A "one-to-one" pattern was found in relation to two peripentonal hexons, "one-to-two" to two of the three neighbouring hexons and "two-to-two" to one hexon. "One-to-two" orientation is the general rule in the GONs. The mutual orientation between the hexons of the neighbouring GONs being in connection with each other and that of the polypeptide subunits of the peripentonal hexons is characterized by the regular alternation of the "one-to-two", "one-to-one" and "two-to-two" orientation. The mutual orientation between the hexons at different points of the capsid has been studied in model experiments and was characterized by the angle enclosed by the longitudinal axis of the given hexon and that of the other hexon in open position towards the virion surface, if the longitudinal axis of the hexons of the triangular faces are perpendicular to the plane of the face and those of the edge-hexons perpendicular to the plane of the edge and the longitudinal axis of the penton faces in radial direction the centre of the virion. In this way the longitudinal axes of the peripentonal hexons enclose with that of the penton an angle of approximately 32 degrees and with each other approximately 36 degrees. The longitudinal axis of the edge-forming hexons shows a deviation of approximately 21 degrees in relation to the longitudinal axes of hexons situated on the neighbouring triangular faces. We present on a tentative virus model the mutual rotational and spatial orientation of all the polypeptide subunits of the adenovirus-building hexon capsomers. This corresponds to the two-, three- and fivefold rotational symmetry characteristic of the icosahedral capsid.

Adenoviruses, Human↗
PubMed1996

Mutations at the capsid-nucleocapsid cleavage site of gag polyprotein of Moloney murine leukemia virus abolish virus infectivity.

Capsid protein CAp30 and nucleocapsid protein NCp10 of Moloney murine leukemia virus (MoMuLV) are the 2 major proteic components of the virion core and are generated by processing of the gag polyprotein precursor, Pr65gag, by the viral protease. In the virion core, several hundred NCp10 molecules are bound to the genomic RNA dimer forming the nucleocapsid structure. In the course of virus assembly, NC protein, as the mature NCp10 and/or as the gag precursor, appears to direct genomic RNA packaging. In vitro, NCp10 has nucleic acid binding and annealing activities and promotes viral RNA dimerization and the annealing of replication primer tRNAPro to the primer binding site (PBS) which is necessary for the initiation of reverse transcription. To investigate whether maturation of NCp10 is required for virus formation, we substituted charged residues for the hydrophobic amino acids at the capsid-nucleocapsid protein cleavage site in order to prevent maturation of NCp10. Here we report that these mutations abolished maturation of capsid protein CAp30 and NCp10 by the viral protease in vitro. When these mutations were introduced into an infectious MoMuLV molecular clone, Pr65gag precursor was synthesized in transfected cells but virion production was strongly diminished and mutant viruses were not infectious. These results suggest that maturation of NCp10 is required for optimal virion release and production of infectious virus.

Binding Sites↗