Self-assembly of hydrophobin proteins from the fungus Trichoderma reesei: Dissertation

Hydrophobins are small surface active proteins that are produced by filamentous fungi. The surface activity of hydrophobin proteins leads to the formation of a film at the air-water interface and adsorption to surfaces. The formation of these hydrophobin films and coatings is important in many stages of fungal development. Furthermore, these properties make hydrophobins interesting for potential use in technical applications. The surfactant-like properties of hydrophobins from Trichoderma reesei were studied at the air-water interface, at solid surfaces, and in solution. The hydrophobin HFBI was observed to spontaneously form a cohesive film on a water drop. The film was imaged using atomic force microscopy from both sides, revealing a monomolecular film with a defined molecular structure. The use of hydrophobins as surface immobilization carriers for enzymes was studied using fusion proteins of HFBI or HFBII and an enzyme. Furthermore, site-specifically modified variants of HFBI were shown to retain their ability to self-assemble at interfaces and to be able to bind a second layer of proteins by biomolecular recognition. In order to understand the function of hydrophobins at interfaces, an understanding of their overall behavior and self-assembly is needed. HFBI and HFBII were shown to associate in solution into dimers and tetramers in a concentration-dependent manner. The association dynamics and protein-protein interactions of HFBI and HFBII were studied using Förster resonance energy transfer and size exclusion chromatography. It was shown that the surface activity of HFBI is not directly dependent on the formation of multimers in solution.