Behavior of Trichoderma reesei hydrophobins in solution: interactions, dynamics, and multimer formation

Area of Science:

• Biochemistry
• Molecular Biology
• Mycology

Background:

• Filamentous fungi use hydrophobins, small amphiphilic proteins, for environmental adaptation.
• Hydrophobins facilitate fungal structure coating, water surface tension reduction, and surface attachment.
• Hydrophobins self-assemble at interfaces, such as air-water and fungal cellular structures, despite water solubility.

Purpose of the Study:

• Investigate the self-assembly mechanism of Trichoderma reesei hydrophobins HFBI and HFBII in aqueous solutions.
• Determine the oligomeric states and interactions of HFBI and HFBII.
• Elucidate the nature of hydrophobin multimers formed in solution.

Main Methods:

• Förster resonance energy transfer (FRET) for studying protein interactions and assembly.
• Size exclusion chromatography to analyze protein size and multimerization.
• Site-specific labeling of a genetically engineered HFBI variant (NCys-HFBI) for FRET experiments.

Main Results:

• HFBI exhibits concentration-dependent multimerization, transitioning from monomers to tetramers.
• At low concentrations, HFBI and HFBII interactions favor homodimers.
• At higher concentrations, heterotetramers of HFBI and HFBII are formed.

Conclusions:

• Hydrophobins in aqueous solutions form stable multimers through hydrophobic interactions.
• Hydrophobin multimers possess defined sizes and involve specific protein-protein interactions, distinct from detergent micelles.
• The findings support a model of hydrophobin self-assembly driven by specific intermolecular forces.