Redox sensitive protein droplets from recombinant oleosin.

Area of Science:

• Biomaterials Science
• Protein Engineering
• Synthetic Biology

Background:

• Protein engineering allows for the creation of materials with designer functionality.
• Oleosin, a plant surfactant protein, naturally phase separates into liquid droplets below a critical temperature.
• This phase separation is driven by a hydrophobic domain, similar to naturally occurring membrane-less organelles.

Purpose of the Study:

• To engineer a protein with tunable phase separation properties.
• To introduce two control motifs for protein droplet formation and dissolution.
• To explore applications in controlled release systems and synthetic protocells.

Main Methods:

• Introducing a cysteine residue into the oleosin protein via sequence mutations.
• Investigating the effect of cysteine on phase separation concentration and transition temperature.
• Utilizing reducing agents to induce rapid dissolution of protein droplets.
• Tuning transition temperature by altering cysteine location or blending protein variants.

Main Results:

• The introduction of cysteine into oleosin altered its phase separation behavior.
• Cysteine-containing oleosin phase separated at a lower concentration and higher transition temperature.
• Reducing agents effectively dissolved the cysteine-containing oleosin droplets.
• The transition temperature was successfully tuned by modifying cysteine position and blending mutants.

Conclusions:

• Engineered oleosin provides a novel method for controlling protein droplet formation and dissolution.
• This system offers tunable sensitivity to reducing conditions for applications like drug delivery.
• The engineered protein serves as a mimic for membrane-less organelles in synthetic protocell research.