HYDROPHOBIN STRUCTURES: TWO FORMS
AND TWO FACES
Both class I and class II hydrophobins are secreted in a soluble
form, and this form of the protein is stable when not in contact
with an interface. For some hydrophobins, the only soluble
form that has been observed is monomeric (e.g., EAS),26
whereas for others, dimers or tetramers are observed under
particular solution conditions (DewA, HFBI/II, and SC3).27–29
Contact with a hydrophobic:hydrophilic boundary results in
the conversion of the hydrophobin into its assembled form,
and the amphipathic monolayer can deposit on either the
hydrophobic face or hydrophilic face (Figure 4).30 Such a deposition
has the effect of reversing the wettability of the surface.
For example, a hydrophobic surface can be rendered hydrophilic
by treatment with hydrophobin.30 The interface-directed
self-assembly and amphipathic nature of hydrophobin monolayers
have led to them being proposed as coatings for biotechnology
and biomedical applications. One advantage of using a
protein-based coating is the possibility for functionalization
through genetic modification of the sequence or subsequent
attachment of ligands onto specific amino acids. However, the