Identification of a novel envelope protein (VP187) gene from shrimp white spot syndrome virus

A novel protein from white spot syndrome virus (WSSV) was identified to match an open reading frame (wsv209) of WSSV genome by combining SDS-PAGE with mass spectrometry. This ORF contained 4818 bp, encoding 1606 aa. The apparent molecular mass of the protein from WSSV virions on SDS-PAGE gel is 187 kDa, so it was named VP187 and its gene was termed vp187. Temporal transcription analysis revealed that vp187 was a late gene. To characterize VP187, a segment of the vp187 gene (vp187p) was cloned into pET-GST vector and expressed as a fusion protein with glutathione S-transferase (GST) in Escherichia coli strain BL21 (DE3). Specific antibody was raised using the purified fusion protein (GST-VP187P). Western blot analysis showed that the mouse anti-GST-VP187P serum reacted specifically with VP187 present either in the WSSV virions or in the viral envelopes, and did not react with fractions of the viral nucleocapsids. VP187 was proved to locate in the WSSV virions as an envelope protein using immunoelectron microscopy.