Characterization of a Basidiomycota hydrophobin reveals the structural basis for a high-similarity Class I subdivision

Abstract

Class I hydrophobins are functional amyloids secreted by fungi. They self-assemble into organized films at interfaces producing structures that include cellular adhesion points and hydrophobic coatings. Here, we present the first structure and solution properties of a unique Class I protein sequence of Basidiomycota origin: the Schizophyllum commune hydrophobin SC16 (hyd1). While the core β-barrel structure and disulphide bridging characteristic of the hydrophobin family are conserved, its surface properties and secondary structure elements are reminiscent of both Class I and II hydrophobins. Sequence analyses of hydrophobins from 215 fungal species suggest this structure is largely applicable to a high-identity Basidiomycota Class I subdivision (IB). To validate this prediction, structural analysis of a comparatively distinct Class IB sequence from a different fungal order, namely the Phanerochaete carnosa PcaHyd1, indicates secondary structure properties similar to that of SC16. Together, these results form an experimental basis for a high-identity Class I subdivision and contribute to our understanding of functional amyloid formation.

Pichia pastoris is a Suitable Host for the Heterologous Expression of Predicted Class I and Class II Hydrophobins for Discovery, Study, and Application in Biotechnology

“…Similarity emerges when examining hydrophobin classes individually. While Class II sequences are relatively well-conserved, it is in fact Class I hydrophobins that share little to no similarity despite the shared solution and interfacial properties described above [ 25 ]. Our recent work explains the high diversity of Class I sequences [ 25 ].…”

“…While Class II sequences are relatively well-conserved, it is in fact Class I hydrophobins that share little to no similarity despite the shared solution and interfacial properties described above [ 25 ]. Our recent work explains the high diversity of Class I sequences [ 25 ]. To better contextualize the primary structures studied herein, we provide a visual representation of this analysis (i.e., a sequence alignment principal component analysis) as it was conducted in [ 25 ] in Figure 2 .…”

Self‐assembly of two hydrophobins from marine fungi affected by interaction with surfaces

“…HFBs are divided into two classes: Class I HFBs are able to assemble into very stable amphipathic mono‐layers, characterized by an amyloid‐like fibril morphology, (Gandier et al, ; Gravagnuolo et al, ; Macindoe et al, ) that can only be depolymerized using pure trifluoroacetic (TFA) or formic acid, while class II HFBs layers lack the fibril structure and can be solubilized with organic solvents and detergents (Lo et al, ). Only a few proteins belonging to Class I HFBs have been analyzed so far and they show quite different self‐assembling mechanisms (Gandier et al, ; Gravagnuolo et al, ). We have focused our work on the discovery of new Class I HFBs, (Armenante et al, ) and the characterization of their self‐assembling (Gravagnuolo et al, ; Longobardi et al, ) to enable modern biotechnological applications (Gravagnuolo et al, ,; Kaur et al, ; Longobardi et al, , ; Patel et al, ; Piscitelli et al, ,; Politi et al, , ).…”

“…HFBs are divided into two classes: Class I HFBs are able to assemble into very stable amphipathic mono-layers, characterized by an amyloid-like fibril morphology, (Gandier et al, 2017;Gravagnuolo et al, 2016a;Macindoe et al, 2012) that can only be depolymerized using pure trifluoroacetic (TFA) or formic acid, while class II HFBs layers lack the fibril structure and can be solubilized with organic solvents and detergents (Lo et al, 2014). Only a few proteins belonging to Class I HFBs have been analyzed so far and they show quite different self-assembling mechanisms (Gandier et al, 2017;Gravagnuolo et al, 2016b).…”

Applications of Functional Amyloids from Fungi: Surface Modification by Class I Hydrophobins

“…The propensity of class I HFBs to self-assemble and the presence of disorder portions in their soluble forms, has precluded the achievement of crystals suitable for X-ray crystallography. However 3D structures of soluble class I HFBs have been obtained by nuclear magnetic resonance (NMR) studies for the EAS from Neurospora crassa [ 9 ], DewA from the fungus Aspergillus nidulans [ 14 ], MPG1 from the fungus Magnaporthe oryzae [ 15 ], and very recently for SC16 from Schizophyllum commune [ 16 ].…”