Identification of the lymantria dispar nucleopolyhedrovirus envelope fusion protein provides evidence for a phylogenetic division of the Baculoviridae.
The complete genome sequences of a number of diverse members of the Baculoviridae including both nucleopolyhedroviruses (NPVs) and granuloviruses (GVs) revealed that they lack a homolog of GP64, the envelope fusion protein of the budded form of Autographa californica multinucleocapsid NPV (AcMNPV) and its close relatives. Computer-assisted analyses of the genome of one of these viruses, Lymantria dispar MNPV (LdMNPV), revealed a single open reading frame (ld130) whose product had the predicted properties of a membrane protein. Characterization of the localization of the products of the full-length ld130 gene and of an ld130-enhanced green fluorescent protein gene (egfp) fusion using both immunofluorescence and fluorescence microscopy revealed that LD130 accumulates at the plasma membranes of cells infected with LdMNPV or transfected with ld130-egfp. In addition, cells transfected with either ld130 or ld130-egfp or infected with wild-type virus undergo membrane fusion at pH 5. Western blot analyses indicate that LD130 is present in infected cells as an 83-kDa protein and is also present in budded virions as a protein doublet containing bands of 81 and 83 kDa. Tunicamycin treatment of infected cells resulted in an immunoreactive band of about 72 kDa, indicating that LD130 is N-glycosylated. Whereas the distribution of gp64 appears to be confined to a relatively closely related group of NPVs, homologs of ld130 are present in a diverse number of both NPVs and GVs. This suggests that LD130 may be the primordial baculovirus envelope fusion protein.
Pearson
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MN
Department of Microbiology, Oregon State University, Corvallis 97331-3804, USA.
Groten
C
C
Rohrmann
G F
GF
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D008561:Membrane Fusion / Q000502:physiology*; D008856:Microscopy, Fluorescence / Q000379:methods; D009036:Moths / Q000821:virology; D017924:Nucleopolyhedroviruses / Q000145:classification / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D014760:Viral Fusion Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D014760:Viral Fusion Proteins