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    Structural Hierarchy in Molecular Films of Two Class II Hydrophobins

    Year: 2003

    Journal: Biochemistry 2003, 42, 5253-5258, 20111221

    Authors: Arja Paananen, Elina Vuorimaa, Mika Torkkeli, Merja Penttilä, Martti Kauranen, Olli Ikkala, Helge Lemmetyinen, Ritva Serimaa, and Markus B. Linder

    Organizations: VTT Biotechnology, Technical Research Centre of Finland, P.O. Box 1500, FIN-02044 VTT, Espoo, Finland; Institute of Materials Chemistry, P.O. Box 541, and Department of Physics, Tampere University of Technology, FIN-33101 Tampere, Finland; Department of Physical Sciences, University of Helsinki, FIN-00014 Helsinki, Finland; and Department of Engineering, Physics, and Mathematics, Helsinki University of Technology, P.O. Box 2200, FIN-02015 HUT, Espoo, Finland

    Hydrophobins are highly surface-active proteins that are specific to filamentous fungi. They function as coatings on various fungal structures, enable aerial growth of hyphae, and facilitate attachment to surfaces. Little is known about their structures and structure-function relationships. In this work we show highly organized surface layers of hydrophobins, representing the most detailed structural study of hydrophobin films so far. Langmuir-Blodgett films of class II hydrophobins HFBI and HFBII from Trichoderma reesei were prepared and analyzed by atomic force microscopy. The films showed highly ordered two-dimensional crystalline structures. By combining our recent results on small-angle X-ray scattering of hydrophobin solutions, we found that the unit cells in the films have dimensions similar to those of tetrameric aggregates found in solutions. Further analysis leads to a model in which the building blocks of the two-dimensional crystals are shape-persistent supramolecules consisting of four hydrophobin molecules. The results also indicate functional and structural differences between HFBI and HFBII that help to explain differences in their properties. The possibility that the highly organized surface assemblies of hydrophobins could allow a route for manufacturing functional surfaces is suggested.