Characterization of Structural and Functional Properties of Class IB Hydrophobins

Abstract

Hydrophobins are low molecular weight self-assembling proteins secreted by fungi and are active at hydrophobic-hydrophilic interfaces. Hydrophobins may undergo structural rearrangement and oligomerize to form rodlets, which are an insoluble functional amyloid. To better understand which sequence characteristics determine hydrophobin properties, I have characterized the structure and properties of class IB hydrophobins from various fungi: Serpula lacrymans (SL1), Wallemia ichthyophaga (WI1), and Phanerochaete carnosa (PC1). I determined the high-resolution structure of each hydrophobin using NMR spectroscopy. This revealed that these hydrophobins all share structural features despite their dissimilar sequences. The core conserved feature is a four strand anti-parallel β-sheet that is connected by three loop sequences (L1-L3). In all hydrophobins the β-sheet folds upon itself to form a β-barrel structure. Spectroscopic amyloid formation assays indicate that each hydrophobin has differing propensities to form rodlets. Overall, this work establishes a correlation between the sequence, structure, and self-assembly properties of hydrophobins.