title: Characterization of the ectromelia virus serpin, SPI-2.
abstract: Poxviruses encode multiple proteins that enable them to evade host responses. Among these are serine protease inhibitors (serpins). One of the earliest serpins described, cowpox virus crmA, acts to inhibit inflammation and apoptosis. crmA homologous serpins, known as SPI-2, are conserved in rabbitpox, vaccinia and variola viruses. Here, we describe the characterization of ectromelia virus (EV) SPI-2. EV SPI-2 encodes a protein of approximately 38 kDa showing >94% identity with other poxviral homologues. Conservative changes in amino acid sequence were found within the reactive site loop and the serpin backbone. Like crmA, transient expression of SPI-2 protected cells from tumour necrosis factor-mediated apoptosis and inhibited the activity of caspases-1 and -8 but not caspases-3, -6 or granzyme B. Overall, this study demonstrates that EV SPI-2 is functionally similar to crmA, based on in vitro assays.
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Parkville 3010, Australia1.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Turner
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Melbourne 3050, Australia2.
authors.forename: John
authors.initials: J
authors.lastname: Silke
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Parkville 3010, Australia1.
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Kenshole
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Parkville 3010, Australia1.
authors.forename: Janet
authors.initials: J
authors.lastname: Ruby
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D053148:Caspase 3; D053178:Caspase 6; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D017124:Conserved Sequence; D015853:Cysteine Proteinase Inhibitors / Q000096:biosynthesis / Q000235:genetics*; D004481:Ectromelia virus / Q000737:chemistry* / Q000235:genetics; D053804:Granzymes; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000378:metabolism; D015843:Serpins / Q000096:biosynthesis / Q000235:genetics*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014764:Viral Proteins; D015003:Yeasts
chemical_list: D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D015843:Serpins; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins; C074641:interleukin-1beta-converting enzyme inhibitor; D053804:Granzymes; D012697:Serine Endopeptidases; D053148:Caspase 3; D053178:Caspase 6; D053181:Caspase 8; D053453:Caspase 9