A designed, phase changing RTX-based peptide for efficient bioseparations.

Area of Science:

• Biochemistry and Molecular Biology
• Protein Engineering and Bioseparations

Background:

• Chromatography, a standard protein purification technique, is often expensive and time-consuming.
• Stimulus-responsive tags offer an alternative, but typically require harsh conditions for precipitation.
• There is a need for gentler, more efficient methods for protein purification.

Purpose of the Study:

• To develop a novel, gentle, and reversible precipitation method for protein purification.
• To engineer a synthetic peptide tag that responds to mild stimuli, specifically calcium ions.
• To demonstrate the efficacy of this tag in purifying various recombinant proteins.

Main Methods:

• Designed a synthetic peptide based on the natural repeat-in-toxin (RTX) domain.
• Fused the calcium-responsive peptide tag to maltose binding protein (MBP) and other target proteins (GFP, β-lactamase, AdhD).
• Induced reversible precipitation using calcium ions and recovered purified proteins via protease cleavage.

Main Results:

• The calcium-responsive tag successfully induced reversible precipitation of fusion proteins under mild conditions.
• Efficient purification of maltose binding protein (MBP) and MBP-fusion proteins (GFP, β-lactamase, AdhD) was achieved.
• Protease cleavage of the tag allowed for the recovery of pure and active target proteins.

Conclusions:

• A novel, gentle, calcium-responsive peptide tag provides an effective alternative to traditional chromatography for protein purification.
• This method facilitates the purification of diverse proteins, including enzymes and fluorescent proteins.
• The tag's reversible precipitation and subsequent cleavage enable efficient recovery of active target proteins.