Isolation, Purification And Characterization Of A DNase-like Protein From Musca Domestic Larva

A new DNase-like protein named as LP was isolated and purified from body of the fifth day's Musca Domestic larva by amonium sulfate precipitation, DE-52 and Sephadex G-75 chromatography.The main properties of LP were as followed: The molecular weight identified by SDS-PAGE was about 85kDa. The isoelectric point by Isoelectric Focusing Electrophoresis was 4.2. Mg2+ was essential to the activity of LP, but with the increase of its concentration, the activity would be decreased. The optimal concentration of Mg2+ was 3-16mmol/L. EDTA was a inhibitor of LP s activity. When the concentration of EDTA was up to 12.5mmol/L, the activity would be completely inhibited. In addition, the optimal pH and temperature for LP while cutting plasmids or chromosomal DNA was 6.0 - 8.5 and 37C-40C, respectively.LP was of stability in boiling water for at least half an hour. The bioactivity of LP was that it could hydrolize some plasmid DNAs as well as chromosomal DNAs, which was different from that of the restricted endonuclease or the exonuclease. However, the mechanism of hydrolysis had not been clear as yet.