Characterization of a Highly Conserved Baculovirus Structural Protein That Is Specific for Occlusion-Derived Virions

A highly conserved baculovirus late gene calledodvp-6ewas shown to be a structural protein that is specific for occlusion-derived virus (ODV) envelopes. The complete sequence of this gene is presented for bothOrgyia pseudotsugatanuclear polyhedrosis virus (OpMNPV) andCydia pomonellagranulosis virus (CpGV). The predicted sizes of the OpMNPV and CpGV ODVP-6E are 40, 241, and 38,655 respectively. The OpMNPVodvp-6egene was transcriptionally mapped and was shown to initiate from a consensus late gene motif, TTAAG, and is expressed from 18–120 hr postinfection. Polyclonal antiserum was generated against a bacterial fusion protein and used to analyze the cellular steady-state levels of ODVP-6E and to determine if this protein was a component of either budded virus (BV) or ODV. Western blots showed that ODVP-6E is a component of the ODV but not BV. This was confirmed by immunoelectron microscopy of ODV fromAutographa californicaNPV (AcMNPV) which localized ODVP-6E to the ODV envelope. The sequences of theodvp-6egene from the baculovirusesChoristoneura fumiferanaNPV (CfMNPV), AcMNPV, andHelicoverpa zeaNPV (HzSNPV) were obtained from GenBank. Comparisons of the predicted amino acid sequences of OpMNPV, CpGV, AcMNPV, CfMNPV, and HzSNPV show that there are two possible membrane-spanning domains and a cysteine-rich domain that are conserved in all of the proteins.