Cloning, characterization, and phylogenetic analysis of a shrimp white spot syndrome virus gene that encodes a protein kinase

An open reading frame (ORF) that encodes a 715-amino-acid polypeptide was f ound in an 8421-bp EcoR1 fragment of the shrimp white spot syndrome virus ( WSSV) genome. The polypeptide shows significant homology to eukaryotic seri ne/threonine protein kinase (PK) and contains the major conserved subdomain s for eukaryotic protein kinases. Coupled in vitro transcription and transl ation generated a protein having an apparent molecular mass of about 87 kDa according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fo r transcriptional analysis of the pk gene, total RNA was isolated from WSSV -infected shrimp at different times after infection. Northern blot analysis with pk-specific riboprobe found a major and a minor transcript of 2.7 and 5.7 kb, respectively. Rapid amplification of the 5' cDNA ends of the major 2.7-kb pk transcript showed that there were two transcriptional initiation sites located at nucleotide residues -38(G) and -39(G) relative to the ATG translational start codon. Temporal expression analysis by RT-PCR indicate d that the transcription of the pk gene started 2 h after infection and con tinued for at least 60 h. Phylogenetic analysis showed that WSSV protein ki nase does not have any close relatives and does not fall into any of the ma jor protein kinase groups. (C) 2001 Academic Press.