Modulating Weak Protein-Protein Cross-Interactions by the Addition of Free Amino Acids at Millimolar Concentrations

Area of Science:

• Biochemistry
• Physical Chemistry

Background:

• Protein-protein interactions (PPIs) are crucial in biological systems.
• Understanding and controlling PPIs is vital for applications in food and pharmaceuticals.

Purpose of the Study:

• To quantify weak PPIs in solution using cross-interaction chromatography (CIC) and surface plasmon resonance (SPR).
• To investigate the modulatory effect of free amino acids on PPIs.
• To assess the impact of these modulations on protein binding affinity and structure.

Main Methods:

• Cross-interaction chromatography (CIC) to determine the second osmotic virial cross-interaction coefficient (B23).
• Surface plasmon resonance (SPR) to measure protein binding affinity.
• Analysis of interactions between lysozyme (Lys), bovine serum albumin (BSA), and protein isolates (whey, canola) with and without amino acids.

Main Results:

• Amino acids (proline, glutamine, arginine) increase PPI repulsion at millimolar concentrations.
• B23 values increased significantly with amino acid addition, indicating weaker attractive interactions.
• SPR showed binding affinity changes up to 3 orders of magnitude (mM to M range) with glutamine.
• Protein secondary structure remained unaltered.

Conclusions:

• Free amino acids are effective modulators of PPIs at low, millimolar concentrations.
• This modulation can significantly alter protein binding affinities.
• The findings have potential applications in the food and pharmaceutical industries for controlling protein behavior.