Arch Virol (2003) 148: 345–355
Involvement of the terminus of grouper betanodavirus
capsid protein in virus-like particle assembly
M. W. Lu and C. S. Lin
Institute of Marine Resources, National Sun Yat-Sen University,
Received June 7, 2002; accepted August 7, 2002
Published online October 21, 2002
Summary. Dragon grouper, Epinephelus lanceolatus, nervous necrosis virus
(DGNNV) consists of 180 copies of capsid protein that encapsulates a bipartite
genome of single-stranded(+)RNAs. Expressingthe open readingframe (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 assem-
bly, 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.
Members of the genus Betanodavirus infects more than 20 species of ﬁsh in
Asia , Europe [3, 14], and Australia . The infection causes nerve cell
necrosis, encephalopathy and retinopathy, accompanied with abnormal swimm-
ing behavior, dark color, and massive mortality in hatchery-reared larvae and
Piscine nodaviruses are members of genus Betanodavirus and typically in-
clude ∼3.1 kb (+)RNA1 and ∼1.4 kb (+)RNA2. The sequences of two genomic
RNAs of the striped jack nervous necrosis virus (SJNNV) [9, 10] and greasy
grouper nervous necrosis virus (GGNNV)  have been documented. The se-
quences of the RNA2 of the dicentrarchus labrax encephalitis virus (DlEV) , the
Atlantic halibut virus (AHV) , and two grouper viruses (malabaricus grouper
MGNNV and dragon grouper E. lanceolatus DGNNV)  have also been deter-
mined. The large genomic RNA1 presumably encodes the viral replicase, while
the small genome RNA2 has been demonstrated to encode the capsid protein .