Molecular Characterization of a Nuclease Gene of Chlorella Virus SS-2

Park, Yun Jung; Jung, Sang Eun; Choi, Tae Jin

The Plant Pathology Journal 2009;25(1):47-53.
Published online March 31, 2009.

Molecular Characterization of a Nuclease Gene of Chlorella Virus SS-2

Yun Jung Park, Sang Eun Jung, Tae Jin Choi

Abstract

Sequence analysis of the Chlorella virus SS-2 revealed one putative nuclease gene that is 807 bp long and encodes a 31kDa protein. Multiple sequence alignment analysis reveals the presence of highly conserved PD-(D/ E)XK residues in the encoded protein. The gene cloned into an expression vector was expressed as a His-tagged fusion protein in chaperone containing pKJE7 cells. The recombinant protein was purified using a His-Trap chelating HP column and used for functional analysis. Exonuclease activity of the SS-2 nuclease was detected when the DNA substrates, such as linear ssDNA, PCR amplicon, linear dsDNA with 5`-overhang ends, 3`- overhang ends, or blunt ends were used. Covalently closed circular DNA was also degraded by the SS-2 recombinant protein, suggesting that the SS-2 nuclease has an endonuclease activity. Stable activity of SS-2 nuclease was observed between 10

Key Words: algal virus, Chlorella virus, nuclease gene, recombinant protein