Search results for "Capsomere"
showing 8 items of 8 documents
Organization of the major and minor capsid proteins in human papillomavirus type 33 virus-like particles.
1995
The organization of the major (L1) and minor (L2) proteins in the human papillomavirus capsid is still largely unknown. In this study we analysed the disulphide bonding between L1 proteins and the association of L2 proteins with capsomers using virus-like particles obtained in insect cells by co-expression of the L1 and L2 genes of human papillomavirus type 33. About 50% of the L1 protein molecules in these particles (1.29 g/cm3) formed disulphide-bonded trimers. Reduction of the intermolecular disulphide bonds by dithiothreitol (DTT) treatment caused disassembly of virus-like particles into capsomers. This indicates that disulphide bonds between capsomers at the threefold symmetry position…
The Minor Capsid Protein VP11 of Thermophilic Bacteriophage P23-77 Facilitates Virus Assembly by Using Lipid-Protein Interactions
2015
ABSTRACT Thermus thermophilus bacteriophage P23-77 is the type member of a new virus family of icosahedral, tailless, inner-membrane-containing double-stranded DNA (dsDNA) viruses infecting thermophilic bacteria and halophilic archaea. The viruses have a unique capsid architecture consisting of two major capsid proteins assembled in various building blocks. We analyzed the function of the minor capsid protein VP11, which is the third known capsid component in bacteriophage P23-77. Our findings show that VP11 is a dynamically elongated dimer with a predominantly α-helical secondary structure and high thermal stability. The high proportion of basic amino acids in the protein enables electrost…
Heparan sulfate proteoglycans interact exclusively with conformationally intact HPV L1 assemblies: basis for a virus-like particle ELISA.
2004
In this article, we demonstrate that interaction of human papillomavirus-like particles (HPV-VLPs) with the putative glucosaminoglycan binding receptor is strictly dependent on conformational integrity. Such conformations are present on VLPs and capsomeres but not on monomers of the major capsid protein, L1, confirming reports that capsomeres can induce virus-neutralizing antibodies. Furthermore, we show the suitability of this specific interaction for development of VLP-based enzyme-linked immunosorbent assays (ELISAs), using heparin for indirect coupling of VLPs to microtiter plates, which may add an intrinsic quality control. This avoids presentation of linear, often highly cross-reactiv…
Surface-exposed Amino Acid Residues of HPV16 L1 Protein Mediating Interaction with Cell Surface Heparan Sulfate
2007
Efficient infection of cells by human papillomaviruses (HPVs) and pseudovirions requires primary interaction with cell surface proteoglycans with apparent preference for species carrying heparan sulfate (HS) side chains. To identify residues contributing to virus/cell interaction, we performed point mutational analysis of the HPV16 major capsid protein, L1, targeting surface-exposed amino acid residues. Replacement of lysine residues 278, 356, or 361 for alanine reduced cell binding and infectivity of pseudovirions. Various combinations of these amino acid exchanges further decreased cell attachment and infectivity with residual infectivity of less than 5% for the triple mutant, suggesting …
Induction of Type-Specific Neutralizing Antibodies by Capsomeres of Human Papillomavirus Type 33
2001
Abstract The immunogenicity of capsomeres of human papillomavirus type 33 was evaluated in a dose–response analysis. Capsomeres were obtained free of capsids by expression of L1 carrying the single point mutation C427S. Neutralizing antibodies were detected using an in vitro pseudoinfection assay. Capsomeres induced type-specific, neutralizing antibodies in mice even in the absence of adjuvant. The neutralization titers of immune sera raised without adjuvant were 10- to 20-fold lower than those of antisera to virus-like particles, but virtually identical using Freund's adjuvant. These data indicate that capsomeres may substitute for virus-like particles in future vaccines when used with an …
Binding and internalization of human papillomavirus type 33 virus-like particles by eukaryotic cells
1995
Infection of cells by human papillomaviruses (HPVs) associated with malignant genital lesions has not been studied because of the lack of an in vitro system and the unavailability of virions. We have now used virus-like particles (VLPs) of HPV type 33 to analyze the initial events in the interaction of the HPV capsid with cell lines. Binding of VLPs to HeLa cells was observed in biochemical assays and by immunofluorescence. VLP binding was inhibited by antisera raised against VLPs but not by monoclonal antibodies recognizing either L1 or L2 epitopes accessible on VLPs. Under saturating conditions, approximately 2 x 10(4) VLPs were bound per cell, with a dissociation constant of about 100 pM…
DNA-induced structural changes in the papillomavirus capsid.
2001
ABSTRACT Human papillomavirus capsid assembly requires intercapsomeric disulfide bonds between molecules of the major capsid protein L1. Virions isolated from naturally occurring lesions have a higher degree of cross-linking than virus-like particles (VLPs), which have been generated in eukaryotic expression systems. Here we show that DNA encapsidation into VLPs leads to increased cross-linking between L1 molecules comparable to that seen in virions. A higher trypsin resistance, indicating a tighter association of capsomeres through DNA interaction, accompanies this structural change.
Papillomavirus assembly requires trimerization of the major capsid protein by disulfides between two highly conserved cysteines.
1998
ABSTRACT We have used viruslike particles (VLPs) of human papillomaviruses to study the structure and assembly of the viral capsid. We demonstrate that mutation of either of two highly conserved cysteines of the major capsid protein L1 to serine completely prevents the assembly of VLPs but not of capsomers, whereas mutation of all other cysteines leaves VLP assembly unaffected. These two cysteines form intercapsomeric disulfides yielding an L1 trimer. Trimerization comprises about half of the L1 molecules in VLPs but all L1 molecules in complete virions. We suggest that trimerization of L1 is indispensable for the stabilization of intercapsomeric contacts in papillomavirus capsids.