Protein Stabilization by Alginate Binding and Suppression of Thermal Aggregation

Area of Science:

• Biochemistry
• Polymer Science
• Drug Delivery

Background:

• Proteins require stabilization for applications like drug delivery.
• Alginate is commonly used for protein encapsulation, but its mechanism of action is unclear.
• Understanding alginate's impact on protein stability is crucial for optimizing its use.

Purpose of the Study:

• To investigate the mechanisms by which alginate affects protein folding stability and aggregation.
• To determine if alginate's effects are due to direct interactions or polymer crowding.
• To assess the protein-dependent nature of alginate's stabilizing effects.

Main Methods:

• Utilized a fluorescence-based conformational reporter assay.
• Monitored two proteins: phosphoglycerate kinase (PGK) and hPin1 WW domain.
• Assessed protein stability and aggregation across varying temperatures and alginate concentrations.

Main Results:

• Alginate increased protein folding stability, with stabilization varying significantly between proteins (e.g., PGK up to 14.5 °C, WW domain 3.5 °C).
• Stabilization was greatest at low alginate concentrations and decreased with higher concentrations, ruling out crowding as the primary mechanism.
• Alginate directly interacted with proteins, involving a significant electrostatic component, and suppressed aggregation by irreversibly associating with unfolded proteins.

Conclusions:

• Alginate stabilizes proteins through direct interactions, not polymer crowding.
• The impact of alginate on protein stability is protein-specific and concentration-dependent.
• Alginate's ability to stabilize proteins and prevent aggregation has significant implications for drug delivery and other applications.