Beta-lactoglobulin molten globule induced by high pressure

Area of Science:

• Protein chemistry
• Food science
• Biophysics

Background:

• Beta-lactoglobulin (beta-LG) is a major whey protein.
• Understanding protein structural changes is crucial for food processing and applications.

Purpose of the Study:

• To investigate the structural and conformational changes in beta-lactoglobulin induced by high hydrostatic pressure (HHP).
• To assess the stability of HHP-induced structural modifications in beta-LG.

Main Methods:

• Treatment of beta-LG with HHP (600 MPa, 50°C) for varying durations.
• Analysis using intrinsic and extrinsic fluorescence spectroscopy.
• Circular dichroism (CD) spectroscopy (far-UV and near-UV).
• Urea denaturation titrations.
• Ellman's reagent assay for thiol reactivity.
• Gel electrophoresis (with and without beta-mercaptoethanol).

Main Results:

• HHP treatment induced significant conformational changes in beta-LG.
• Increased accessible aromatic hydrophobicity and decreased aliphatic hydrophobicity were observed.
• Secondary structure shifted from beta-sheets to alpha-helices; tertiary structure was disrupted.
• Pressure-treated beta-LG exhibited noncooperative unfolding, unlike native beta-LG.
• A previously inaccessible thiol group became reactive, leading to S-S linked dimer formation.
• The altered structure formed stable hydrophobic molten globules, persisting for 3 months at 5°C.

Conclusions:

• HHP treatment induces beta-LG into stable hydrophobic molten globule states.
• These structural changes are characterized by altered secondary and tertiary structures and increased hydrophobicity.
• The observed stability suggests potential for controlled modification of beta-LG functionality in food systems.