Constructing Modified Protein-producing Escherichia coli Capable of Autohydrolysing Host Nucleic Acid During Cell Lysis

We used Red recombination system to construct a modified E. coli protein-producing strain capable of autohydrolysing host nucleic acid. E. coli BL21 (DE3), a common protein-producing strain, was used as starting material. The modified E. coli expression host had a staphylococcal nuclease expression cassette within the host chromosome lpxM locus. The Staphylococcus aureus nuclease was expressed as a fusion to the ompA signal peptide, and was translocated to the periplasm of the cell, protecting the host nucleic acid from the toxic activity during growth. The nuclease was released during cell lysis and subsequently hydrolyzed host nucleic acid in the lysate. Results show that the modified strain had sufficient nuclease activity to completely autohydrolyze the host chromosomal DNA and produced same amount of recombinant proteins as the original strain.