Construction of a novel zero background prokaryotic expression vector: potential advantages.

Area of Science:

• Molecular Biology
• Bacteriology
• Protein Engineering

Background:

• The CcdB protein is a well-known inhibitor of DNA gyrase in Escherichia coli.
• Investigating novel toxic sequences can lead to new molecular tools and understanding of bacterial physiology.

Purpose of the Study:

• To characterize a novel toxic DNA sequence derived from the antisense strand of CcdB.
• To explore the potential of this toxic sequence in developing a high-efficiency cloning vector.
• To elucidate the mechanism of toxicity of the novel protein.

Main Methods:

• Cloning and expression of a novel toxic gene sequence in E. coli K12 and BL21.
• Assessment of protein solubility under different expression conditions.
• Construction and evaluation of a prokaryotic cloning/expression vector utilizing the toxic gene.
• Testing the toxicity of the expressed protein on a CcdB-resistant E. coli strain.

Main Results:

• The novel toxic protein (approx. 6 kDa) drastically reduced E. coli K12 growth rate (three orders of magnitude) upon induction.
• Protein solubility varied between E. coli K12 (soluble) and E. coli BL21 (insoluble).
• A highly efficient cloning vector was developed, showing zero background and ~100% cloning efficiency without dephosphorylation.
• The toxic protein impacted CcdB-resistant cells, suggesting a non-DNA gyrase inhibition toxicity mechanism.

Conclusions:

• A novel toxic protein, distinct from CcdB's known function, was identified and characterized.
• This toxic protein is a valuable component for constructing highly efficient prokaryotic cloning vectors.
• The findings suggest a novel toxicity pathway independent of DNA gyrase inhibition.