Charge-based engineering of hydrophobin HFBI: effect on interfacial assembly and interactions

Area of Science:

• Biochemistry
• Materials Science
• Mycology

Background:

• Hydrophobins are extracellular fungal proteins with amphiphilic properties.
• They self-assemble at interfaces, influencing fungal adaptation through adhesion and surface tension reduction.
• Intermolecular interactions are crucial for hydrophobin function, complementing their amphiphilicity.

Purpose of the Study:

• To investigate the structural basis of hydrophobin function using HFBI as a model.
• To understand the role of charged residues in the hydrophilic regions of hydrophobins.
• To elucidate how mutations affect hydrophobin self-assembly, interfacial properties, and macromolecular binding.

Main Methods:

• Site-directed mutagenesis of charged residues in hydrophobin HFBI.
• Analysis of self-assembled layer formation and structure.
• Assessment of solution multimerization, surface adhesion, and secondary protein layer binding.
• Measurement of air-water interface viscoelasticity during protein film formation.

Main Results:

• Mutations in charged residues altered hydrophobin behavior at the air-water interface.
• Specific interactions were identified as key regulators of surface layer formation and protein docking.
• One mutant set exhibited significantly enhanced interfacial elasticity (1.44 N/m).
• Variations in secondary protein layer binding suggest a specific adhesive function.

Conclusions:

• Hydrophobin self-assembly and function are modulated by specific intermolecular interactions involving charged residues.
• HFBI variants demonstrate tunable interfacial elasticity, highlighting potential applications in biomaterials.
• Hydrophobins can serve as specific adhesive layers for immobilizing macromolecules at interfaces.