The fungal cerato-platanin protein EPL1 forms highly ordered layers at hydrophobic/hydrophilic interfaces

Abstract

Cerato-platanin proteins (CPPs) and hydrophobins are two classes of small, secreted proteins that are exclusively found in fungi. CPPs are known as chitin-binding proteins, and were recently also shown to form protein layers at air/water interfaces, but the features of these layers were not investigated on the molecular level yet. In this study, by means of atomic force microscopy (AFM), EPL1, a member of the CPP family was shown to form highly ordered monolayers at a hydrophobic surface/liquid-interface. Furthermore, two new hydrophobins were analysed, and the influence of EPL1 on hydrophobin layers was studied in situ. Hydrophobins are amphiphilic proteins that are able to self-assemble at hydrophobic/hydrophilic interfaces, thereby inverting the polarity of the surface. This renders fungal growth structures such as spores water repellent. The combination of AFM data and wettability experiments led to the conclusion that in presence of both, hydrophobins and EPL1, a previously unknown hybrid layer is formed. This mixed protein layer is on one hand not inverting but enhancing the hydrophobicity of HOPG (highly oriented pyrolytic graphite), typical for EPL1, and on the other hand, it is stable and water insoluble, which is reminiscent of hydrophobin layers.

Foaming, emulsifying and rheological properties of extracts from a co-product of the Quorn fermentation process

“…In particular cerato-platanins from Trichoderma are known to forms dimers [26]. The ceratoplatanin EPL1 from the fungus Trichoderma atroviride was reported to form ordered self-assembled layers at the air/ water interface [9] and hydrophobic/hydrophilic interfaces [27]. The HEX-1 protein was also shown to self-assemble into three-dimensional lattices to form Woronin bodies, which are peroxisome-derived organelles that maintain cellular integrity and prevent cytoplasmic bleeding in response to hyphal wounding and cellular damage by sealing septal pores [28].…”

Cerato-Platanins from Marine Fungi as Effective Protein Biosurfactants and Bioemulsifiers

“…Similar to HFBs, their solutions lead to strong foam formation and they self-assemble at hydrophobic:hydrophilic interfaces into ordered, amphipathic layers [12,13]. However, they are not HFB-like proteins, and some studies indicated that their behavior is opposite to that of HFBs, i.e., it has been reported that the CP EPL1 from Trichoderma atroviride increased the polarity of solutions and surfaces [12,14]. Moreover, structural analysis of CP from Ceratocystis platani revealed that there are significant structural differences between CPs and HFBs, i.e., the surface of the molecule shows no large hydrophobic patch [11].…”

Involvement of Trichoderma harzianum Epl-1 Protein in the Regulation of Botrytis Virulence- and Tomato Defense-Related Genes

“…Proteins from the cerato-platanin (CP) family, such as Sm1/Epl-1 produced by Trichoderma virens and T. atroviride , can form protein biofilms at air–water interfaces. This feature enhances the polarity effects of surfaces and solutions and thus promotes the formation of highly ordered monolayers at hydrophobic surface–liquid interfaces (Frischmann et al, 2013; Bonazza et al, 2015). The structure of CP proteins resembles that of expansins, which do not have an enzymatic function.…”

“…Furthermore, expansin-like proteins are important in the degradation of the plant cell wall by inducing the opening of physical spaces required for the action of cellulolytic enzymes (Baccelli et al, 2014; Castro et al, 2014). Like expansins, CP proteins also bind carbohydrates, which suggest that CP proteins have a similar function and that these proteins can induce the opening of physical spaces in structural components of the fungal cell wall, such as in chitin polymers (Frischmann et al, 2013; Baccelli et al, 2014; Bonazza et al, 2015). CP proteins are also effective elicitors capable of triggering local and systemic plant defense responses (Djonovic et al, 2006, 2007; Seidl et al, 2006; Vargas et al, 2008; Pazzagli et al, 2014).…”