Bicistronic mRNAs to enhance membrane protein overexpression

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Functional overexpression of membrane proteins is critical for structural and functional characterization.
• Achieving high yields of correctly folded membrane proteins remains a significant challenge, often resulting in low expression or misfolded aggregates.

Purpose of the Study:

• To develop an improved method for the functional overexpression of membrane proteins in Escherichia coli.
• To enhance the quantity and quality of membrane proteins for structural and functional studies.

Main Methods:

• Utilizing transcriptional fusions by introducing a small RNA sequence upstream of the target membrane protein gene.
• Generating a bicistronic mRNA to facilitate enhanced protein production.
• Investigating the impact of the upstream RNA sequence and its potential folding on protein yields.

Main Results:

• Observed significant improvements in the quantity and/or quality of expressed membrane proteins for several targets.
• Achieved expression levels compatible with subsequent structural studies.
• Demonstrated that the upstream RNA sequence's folding, rather than its translation, significantly impacts protein yields.

Conclusions:

• Transcriptional fusions offer a viable strategy to overcome challenges in membrane protein overexpression.
• The RNA sequence itself plays a critical role in enhancing protein production, suggesting RNA folding as a key factor.
• This method provides a protease-free alternative to traditional fusion protein approaches for improving membrane protein yields.