Abstract
The serpin SPI-3 and the hemagglutinin (HA) encoded by cowpox virus (CPV) block cell-cell fusion, and colocalize at the cell surface. wtCPV does not fuse cells, but inactivation of either gene leads to fusion. SPI-3 mAb added to wtCPV-infected cells caused fusion, confirming that SPI-3 protein at the cell surface prevents fusion. The SPI-3 mAb epitope mapped to an 85-amino acid region at the C-terminus. Removal of either 44 residues from the SPI-3 C-terminus or 48 residues following the N-terminal signal sequence resulted in fusion. Interaction between SPI-3 and HA proteins in infected cells was shown by coimmunoprecipitation. SPI-3/HA was not associated with the A27L "fusion" protein. SPI-3 and HA were able to associate in uninfected cells in the absence of other viral proteins. The HA-binding domain in SPI-3 resided in the C-terminal 229 residues, and did not include helix D, which mediates cofactor interaction in many other serpins.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Amino Acid Sequence
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Animals
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Antibodies, Monoclonal
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Antibodies, Viral
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Cell Line
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Cell Membrane / virology
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Chlorocebus aethiops
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Cowpox virus / genetics
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Cowpox virus / immunology
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Cowpox virus / pathogenicity*
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Cowpox virus / physiology*
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Epitope Mapping
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Hemagglutinins, Viral / genetics
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Hemagglutinins, Viral / immunology
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Hemagglutinins, Viral / physiology*
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Membrane Fusion / genetics
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Membrane Fusion / physiology
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Models, Molecular
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Molecular Sequence Data
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Mutation
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Protein Conformation
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Recombinant Proteins / genetics
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Recombinant Proteins / immunology
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Recombinant Proteins / metabolism
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Sequence Homology, Amino Acid
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Serpins / chemistry
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Serpins / genetics
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Serpins / immunology
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Serpins / physiology*
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Transfection
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Viral Proteins / chemistry
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Viral Proteins / genetics
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Viral Proteins / immunology
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Viral Proteins / physiology*
Substances
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Antibodies, Monoclonal
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Antibodies, Viral
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Hemagglutinins, Viral
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Recombinant Proteins
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Serpins
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Viral Proteins