Self-assembled hydrophobin protein films at the air-water interface: structural analysis and molecular engineering

Géza Szilvay, Arja Paananen, Katri Laurikainen, Elina Vuorimaa, Helge Lemmetyinen, Jouko Peltonen, Markus Linder

Research output: Contribution to journalArticleScientificpeer-review

122 Citations (Scopus)

Abstract

Hydrophobins are amphiphilic proteins produced by filamentous fungi. They function in a variety of roles that involve interfacial interactions, as in growth through the air-water interface, adhesion to surfaces, and formation of coatings on various fungal structures. In this work, we have studied the formation of films of the class II hydrophobin HFBI from Trichoderma reesei at the air-water interface. Analysis of hydrophobin aqueous solution drops showed that a protein film is formed at the air-water interface. This elastic film was clearly visible, and it appeared to cause the drops to take unusual shapes. Because adhesion and formation of coatings are important biological functions for hydrophobins, a closer structural analysis of the film was made. The method involved picking up the surface film onto a solid substrate and imaging the surface by atomic force microscopy. High-resolution images were obtained showing both the hydrophilic and hydrophobic sides of the film at nanometer resolution. It was found that the hydrophobin film had a highly ordered structure. To study the orientation of molecules and to obtain further insight in film formation, we made variants of HFBI that could be site specifically conjugated. We then used the avidin-biotin interaction as a probe. On the basis of this work, we suggest that the unusual interfacial properties of this type of hydrophobins are due to specific molecular interactions which lead to an ordered network of proteins in the surface films that have a thickness of only one molecule. The interactions between the proteins in the network are likely to be responsible for the unusual surface elasticity of the hydrophobin film.
Original languageEnglish
Pages (from-to)2345-2354
JournalBiochemistry
Volume46
Issue number9
DOIs
Publication statusPublished - 2007
MoE publication typeA1 Journal article-refereed

Fingerprint

Structural analysis
Air
Water
Fungal Structures
Proteins
Trichoderma
Avidin
Atomic Force Microscopy
Elasticity
Biotin
Membrane Proteins
Fungi
Growth
Adhesion
Coatings
Molecules
Molecular interactions
Image resolution
1-(heptafluorobutyryl)imidazole
Atomic force microscopy

Keywords

  • hydrophobins
  • filamentous fungi
  • Trichoderma reesei
  • coatings

Cite this

Szilvay, Géza ; Paananen, Arja ; Laurikainen, Katri ; Vuorimaa, Elina ; Lemmetyinen, Helge ; Peltonen, Jouko ; Linder, Markus. / Self-assembled hydrophobin protein films at the air-water interface: structural analysis and molecular engineering. In: Biochemistry. 2007 ; Vol. 46, No. 9. pp. 2345-2354.
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Self-assembled hydrophobin protein films at the air-water interface: structural analysis and molecular engineering. / Szilvay, Géza; Paananen, Arja; Laurikainen, Katri; Vuorimaa, Elina; Lemmetyinen, Helge; Peltonen, Jouko; Linder, Markus.

In: Biochemistry, Vol. 46, No. 9, 2007, p. 2345-2354.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Self-assembled hydrophobin protein films at the air-water interface: structural analysis and molecular engineering

AU - Szilvay, Géza

AU - Paananen, Arja

AU - Laurikainen, Katri

AU - Vuorimaa, Elina

AU - Lemmetyinen, Helge

AU - Peltonen, Jouko

AU - Linder, Markus

PY - 2007

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N2 - Hydrophobins are amphiphilic proteins produced by filamentous fungi. They function in a variety of roles that involve interfacial interactions, as in growth through the air-water interface, adhesion to surfaces, and formation of coatings on various fungal structures. In this work, we have studied the formation of films of the class II hydrophobin HFBI from Trichoderma reesei at the air-water interface. Analysis of hydrophobin aqueous solution drops showed that a protein film is formed at the air-water interface. This elastic film was clearly visible, and it appeared to cause the drops to take unusual shapes. Because adhesion and formation of coatings are important biological functions for hydrophobins, a closer structural analysis of the film was made. The method involved picking up the surface film onto a solid substrate and imaging the surface by atomic force microscopy. High-resolution images were obtained showing both the hydrophilic and hydrophobic sides of the film at nanometer resolution. It was found that the hydrophobin film had a highly ordered structure. To study the orientation of molecules and to obtain further insight in film formation, we made variants of HFBI that could be site specifically conjugated. We then used the avidin-biotin interaction as a probe. On the basis of this work, we suggest that the unusual interfacial properties of this type of hydrophobins are due to specific molecular interactions which lead to an ordered network of proteins in the surface films that have a thickness of only one molecule. The interactions between the proteins in the network are likely to be responsible for the unusual surface elasticity of the hydrophobin film.

AB - Hydrophobins are amphiphilic proteins produced by filamentous fungi. They function in a variety of roles that involve interfacial interactions, as in growth through the air-water interface, adhesion to surfaces, and formation of coatings on various fungal structures. In this work, we have studied the formation of films of the class II hydrophobin HFBI from Trichoderma reesei at the air-water interface. Analysis of hydrophobin aqueous solution drops showed that a protein film is formed at the air-water interface. This elastic film was clearly visible, and it appeared to cause the drops to take unusual shapes. Because adhesion and formation of coatings are important biological functions for hydrophobins, a closer structural analysis of the film was made. The method involved picking up the surface film onto a solid substrate and imaging the surface by atomic force microscopy. High-resolution images were obtained showing both the hydrophilic and hydrophobic sides of the film at nanometer resolution. It was found that the hydrophobin film had a highly ordered structure. To study the orientation of molecules and to obtain further insight in film formation, we made variants of HFBI that could be site specifically conjugated. We then used the avidin-biotin interaction as a probe. On the basis of this work, we suggest that the unusual interfacial properties of this type of hydrophobins are due to specific molecular interactions which lead to an ordered network of proteins in the surface films that have a thickness of only one molecule. The interactions between the proteins in the network are likely to be responsible for the unusual surface elasticity of the hydrophobin film.

KW - hydrophobins

KW - filamentous fungi

KW - Trichoderma reesei

KW - coatings

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EP - 2354

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

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ER -