A study of the Autographa californica multiple nucleopolyhedrovirus ODV envelope protein p74 using a GFP tag

The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) protein p 74 is associated with the occlusion-derived virus (ODV) envelope. p74 is es sential for oral infectivity of ODV and has been proposed to play a role in midgut attachment and/or fusion. In this study, p74 protein was expressed in-frame with green fluorescent protein (GFP) to create a p74-GFP chimera. The C-terminal GFP portion of the chimera facilitated visualization of the trafficking of p74 in baculovirus-infected Spodoptera frugiperda (Sf-9) cel ls. p74-GFP chimeric proteins localized in the intranuclear ring zone of th e nucleus and were found to co-precipitate with the microvesicle fraction o f cell lysates. A series of truncations of p74 was expressed as p74-GFP chi meras in recombinant baculoviruses. When C-terminal region S580-F645 was de leted from p74, p74-GFP chimera localization became non-specific and chimer as became soluble. p74 region S580-F645 directed GFP to the intranuclear ri ng zone in a similar pattern to full-length p74. The hydrophobic C terminus of p74 plays a role in protein localization and possibly in transmembrane anchoring and insertion.