Structural Characterization of the Hydrophobin SC3, as a Monomer and after Self-Assembly at Hydrophobic/Hydrophilic Interfaces

Marcel L. de Vocht, Karin Scholtmeijer, Eric W. van der Vegte, Onno M.H. de Vries, Nathalie Sonveaux, Han A.B. Wösten, Jean-Marie Ruysschaert, Georges Hadziioannou, Joseph G.H. Wessels, George T. Robillard

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Abstract

Hydrophobins are small fungal proteins that self-assemble at hydrophilic/hydrophobic interfaces into amphipathic membranes that, in the case of Class I hydrophobins, can be disassembled only by treatment with agents like pure trifluoroacetic acid. Here we characterize, by spectroscopic techniques, the structural changes that occur upon assembly at an air/water interface and upon assembly on a hydrophobic solid surface, and the influence of deglycosylation on these events. We determined that the hydrophobin SC3 from Schizophyllum commune contains 16–22 O-linked mannose residues, probably attached to the N-terminal part of the peptide chain. Scanning force microscopy revealed that SC3 adsorbs specifically to a hydrophobic surface and cannot be removed by heating at 100°C in 2% sodium dodecyl sulfate. Attenuated total reflection Fourier transform infrared spectroscopy and circular dichroism spectroscopy revealed that the monomeric, water-soluble form of the protein is rich in β-sheet structure and that the amount of β-sheet is increased after self-assembly on a water-air interface. α-Helix is induced specifically upon assembly of the protein on a hydrophobic solid. We propose a model for the formation of rodlets, which may be induced by dehydration and a conformational change of the glycosylated part of the protein, resulting in the formation of an amphipathic α-helix that forms an anchor for binding to a substrate. The assembly in the β-sheet form seems to be involved in lowering of the surface tension, a potential function of hydrophobins.
Original languageEnglish
Pages (from-to)2059 - 2068
Number of pages10
JournalBiophysical Journal
Volume74
Issue number4
DOIs
Publication statusPublished - 1998

Keywords

  • PROTEIN SECONDARY STRUCTURE
  • CHEMICAL FORCE MICROSCOPY
  • SCHIZOPHYLLUM-COMMUNE
  • FUNGAL HYDROPHOBIN
  • AERIAL HYPHAE
  • ADSORPTION
  • SURFACE
  • SPECTROSCOPY
  • MONOLAYERS
  • PREDICTION

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