%0 Journal Article %A Slack, Jeffrey M. %A Lawrence, Susan D. %T Evidence for proteolytic cleavage of the baculovirus occlusion-derived virion envelope protein P74 %D 2005 %J Journal of General Virology, %V 86 %N 6 %P 1637-1643 %@ 1465-2099 %R https://doi.org/10.1099/vir.0.80832-0 %I Microbiology Society, %X 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. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.80832-0