Characterization of the major capsid protein and cloning of its gene from algal virus PBCV-1.

The major capsid protein (Vp54) from Chlorella virus PBCV-1 is a glycoprotein and the most abundant viral structural protein. The gene encoding Vp54 has been cloned and sequenced. Initially, a region of the gene was amplified using the polymerase chain reaction (PCR) primed with oligonucleotides derived from the N-terminal amino acid sequences of purified protein and cyanogen bromide cleavage fragments. The PCR product was used as a probe to map the location of the gene to PBCV-1 genomic Pstl restriction fragment P8. A 1314-bp open reading frame (ORF) was identified which contained the predicted coding regions from the derived amino acid sequences. The peptide encoded by this ORF had a predicted molecular weight of 48.2 kDa and contained six putative N-linked and 63 putative O-linked glycosylation sites. Primer extension analysis indicated that transcription started 14 bp 5' to the ATG. The gene for Vp54 was transcribed late in infection and this transcript was the most abundant viral RNA present in infected cells.