title: Evidence for proteolytic cleavage of the baculovirus occlusion-derived virion envelope protein P74.
abstract: Baculovirus occlusion-derived virions (ODVs) are released from occlusion bodies by the alkaline environment of the insect midgut. The ODV envelope protein P74 is required for oral infectivity. A soluble form of the Autographa californica multiple nucleopolyhedrovirus P74 protein, P74sol, was engineered as part of a chimeric protein with jellyfish green fluorescent protein (GFP). P74sol-GFP was overproduced by the baculovirus expression system and purified away from the wild-type P74. Brush border membrane vesicles (BBMVs) were prepared from the midguts of third-instar Helicoverpa zea larvae. When P74sol-GFP was incubated under alkaline conditions with BBMVs, a P74sol-GFP product with a smaller molecular mass was produced. Immunoblots indicated that the smaller product was generated by N-terminal cleavage of P74. This cleavage was prevented by soybean trypsin inhibitor. Analysis of the peptide sequences of P74 homologues identified a conserved trypsin cleavage site that could generate the observed P74sol-GFP BBMV-specific cleavage product.
authors.affiliation: USDA/ARS, Insect Biocontrol Laboratory, BARC-West, Bldg 011A, Rm 214, Beltsville, MD 20852-2350, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Slack
authors.affiliation: USDA/ARS, Insect Biocontrol Laboratory, BARC-West, Bldg 011A, Rm 214, Beltsville, MD 20852-2350, USA.
authors.forename: Susan D
authors.initials: SD
authors.lastname: Lawrence
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007915:Lepidoptera / Q000201:enzymology* / Q000821:virology*; D008871:Microvilli / Q000201:enzymology* / Q000821:virology; D017924:Nucleopolyhedroviruses / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: C066445:Ac-gp37 protein, Autographa californica nucleopolyhedrovirus; C109481:Ac-p74 protein, Autographa californica nucleopolyhedrovirus; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; D014357:Trypsin