title: Interactions of hydrophobin proteins in solution studied by small-angle X-ray scattering.
abstract: Hydrophobins are a group of very surface-active, fungal proteins known to self-assemble on various hydrophobic/hydrophilic interfaces. The self-assembled films coat fungal structures and mediate their attachment to surfaces. Hydrophobins are also soluble in water. Here, the association of hydrophobins HFBI and HFBII from Trichoderma reesei in aqueous solution was studied using small-angle x-ray scattering. Both HFBI and HFBII exist mainly as tetramers in solution in the concentration range 0.5-10 mg/ml. The assemblies of HFBII dissociate more easily than those of HFBI, which can tolerate changes of pH from 3 to 9 and temperatures in the range 5 degrees C-60 degrees C. The self-association of HFBI and HFBII is mainly driven by the hydrophobic effect, and addition of salts along the Hofmeister series promotes the formation of larger assemblies, whereas ethanol breaks the tetramers into monomers. The possibility that the oligomers in solution form the building blocks of the self-assembled film at the air/water interface is discussed.
authors.affiliation: Department of Physical Sciences, University of Helsinki, FI-00014 HU, Finland. kaisa.kisko@helsinki.fi
authors.forename: Kaisa
authors.initials: K
authors.lastname: Kisko
authors.forename: Géza R
authors.initials: GR
authors.lastname: Szilvay
authors.forename: Ulla
authors.initials: U
authors.lastname: Vainio
authors.forename: Markus B
authors.initials: MB
authors.lastname: Linder
authors.forename: Ritva
authors.initials: R
authors.lastname: Serimaa
mesh_terms: D001665:Binding Sites; D003198:Computer Simulation; D019281:Dimerization; D005656:Fungal Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D053838:Scattering, Small Angle; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction