Hydrophobins: proteins that change the nature of the fungal surface.

Publisher Summary Hydrophobins were discovered while searching for genes expressed during emergent growth in Schizophyllum commune, and are a novel class of small secreted cysteine-rich proteins of fungi that assemble into amphipathic films when confronted with hydrophilichydrophobic interfaces. The hydrophobicity of the air-exposed surface of the S. commune (SC3) film was as high as that of the surface of aerial hyphae. This process of interfacial self-assembly of a single hydrophobin into a hydrophobic rodlet layer provides a remarkably simple mechanism, by which hyphae and spores obtain a hydrophobic layer at their surface because it is at this surface that the secreted hydrophobin monomers reach the water–air interface and assemble into an amphipathic film. Some hydrophobins form unstable, others extremely stable, amphipathic films. By assembling at a wall–air interface some have been shown to provide for a hydrophobic surface, which has the ultrastructural appearance of rodlets as on aerial hyphae and spores. Some hydrophobins have been shown to assemble into amphipathic films at interfaces between water and oils, or hydrophobic solids, and may be involved in adherence phenomena. It appears that hydrophobins are among the most abundantly produced proteins of fungi, and individual species may contain several genes producing divergent hydrophobins, possibly tailored for specific purposes. Hydrophobins have now been implicated in various developmental processes, such as formation of aerial hyphae, fruit bodies and conidia, and may play essential roles in fungal ecology— including spore dissemination, pathogenesis, and symbiosis. The surfactive properties of hydrophobins and the ability of some of them to form very stable insoluble amphipathic films, which change the wettability of surfaces, also makes them good candidates for technical applications.