Involvement of the terminus of grouper betanodavirus capsid protein in virus-like particle assembly.

Dragon grouper, Epinephelus lanceolatus, nervous necrosis virus (DGNNV) consists of 180 copies of capsid protein that encapsulates a bipartite genome of single-stranded (+)RNAs. Expressing the open reading frame (ORF) of RNA2 in Escherichia coli forms virus-like particles (VLPs) that resembles native virus. Deleting N- and C-termini revealed different impacts on VLP formation. Deletion of 35 or 52 residues at the N-terminus completely ruined the VLP assembly, presumably due to removal of positively charged residues for binding RNAs. When deletions were restricted to 4, 16, or 25 N-terminal residues, the assembly of VLPs remained. The ability of VLP formation diminished when 4 to 11 C-terminal residues were deleted. The termini that can be deleted without seriously destructing the VLPs are 25 and 3 residues at N- and C-termini, respectively.