Biology Reference
In-Depth Information
Comparative analysis of the coat protein genes of five betano-
daviruses has shown that the sequence can be divided into a highly
conserved region and a variable region. In SJNNV, the conserved
region is represented by amino acids 83-216 and the variable region
by amino acids 235-315. Based on this division, the sequences of
MGNNV and DGNNV were compared at the nucleotide level and
amino acid level with the sequences of four other betanodaviruses
of Asian and European origin.
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These viruses were SJNNV from
Japan, DlEV from France, AHV from Norway, and GGNNV from
Singapore. MGNNV and DGNNV viruses were most closely related
to GGNNV. Interestingly, the analysis also revealed that the Japanese
SJNNV differed significantly from its geographical neighbors, the
Taiwanese MGNNV and DGNNV, particularly in the variable region.
In contrast, the geographically proximal European DlEV and AHV
showed a higher degree of similarity with each other and the Taiwanese
viruses. This suggests that host-dependent selection impacts more
significantly on evolution than geographically related conditions such
as water temperature.
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MGNNV and DGNNV have a high concentration of basic amino
acids in the N-terminal 50 residues. Insect nodaviruses contain 15-18
positively charged amino acids, mostly arginines, in the first 50 amino
acids, while MGNNV and DGNNV contain 9 arginine and 6 lysine
residues.
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It is likely that the N-terminal basic arm of the fish virus
coat protein is involved in binding and neutralization of the packaged
RNA and that it is located inside the viral capsid as observed for the
insect viruses. The arginine-rich region that can bind nucleotides with
ionic bonds was coincidently considered as a nuclear internalization
signal, which will be arbitrary possible.
Virus-like Particle Formation
The ORF region of RNA2 encoding the capsid protein of MGNNV
was subcloned into a transfer vector and recombinant baculoviruses
were generated using standard protocols.
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Sf 21 cells were then infected
with the recombinant virus and lysed three days post-infection, and
putative particles in the lysate were concentrated by pelleting through
