Bacterial expression system with tightly regulated gene expression and plasmid copy number

Area of Science:

• Molecular Biology
• Microbial Genetics
• Biotechnology

Background:

• Controlling gene expression and plasmid copy number is crucial for recombinant protein production and genetic studies.
• Existing systems often lack fine-tuning capabilities, leading to issues like toxic gene product instability or inefficient expression.

Purpose of the Study:

• To engineer a new Escherichia coli host/vector system for precise and uniform modulation of gene expression and gamma origin (ori) plasmid copy number.
• To enable independent control over gene expression and gene dosage for cloning and overproducing toxic gene products.

Main Methods:

• Engineered an E. coli strain with arabinose-inducible expression of the Rep protein (pi) on the chromosome, controlling gamma ori plasmid replication.
• Utilized a mutant LacY transporter (LacYA177C) for controlled arabinose uptake, bypassing native uptake and degradation pathways.
• Developed a compatible gamma ori expression vector for tight gene expression regulation.

Main Results:

• Achieved over 100-fold uniform modulation of gamma ori plasmid copy number by adjusting l-arabinose concentration.
• Successfully cloned and overproduced the potent toxin Colicin E3 without its immunity protein, demonstrating system efficacy.
• The system allows independent modulation of gene expression and gene dosage.

Conclusions:

• The engineered E. coli host/vector system provides tight and uniform control over gene expression and plasmid copy number.
• This system is valuable for cloning and overproducing toxic proteins, screening for toxins, and maintaining vectors at precise copy levels.