Self-assembly at Air/Water Interfaces and Carbohydrate Binding Properties of the Small Secreted Protein EPL1 from the fungus Trichoderma atroviride

• Published in: The Journal of biological chemistry Vol. 288; no. 6; pp. 4278 - 4287
• Main Authors: Frischmann, Alexa, Neudl, Susanna, Gaderer, Romana, Bonazza, Klaus, Zach, Simone, Gruber, Sabine, Spadiut, Oliver, Friedbacher, Gernot, Grothe, Hinrich, Seidl-Seiboth, Verena
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08.02.2013; American Society for Biochemistry and Molecular Biology
• Subjects: Carbohydrate-binding Protein; Cerato-platanin; Chitin; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Gene Expression Regulation, Fungal - physiology; Gene Knockdown Techniques; Genome, Fungal - physiology; Hydrophobin; Microbiology; Protein Aggregation; Protein Multimerization - physiology; Protein Self-assembly; Protein Structure, Quaternary; Surface Activity; Trichoderma - chemistry; Trichoderma - genetics; Trichoderma - metabolism; Fungi; Carbohydrate-binding Protein; Protein Self-assembly; Cerato-platanin; Protein Aggregation; Chitin; Hydrophobin; Surface Activity
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M112.427633

The protein EPL1 from the fungus Trichoderma atroviride belongs to the cerato-platanin protein family. These proteins occur only in filamentous fungi and are associated with the induction of defense responses in plants and allergic reactions in humans. However, fungi with other lifestyles also express cerato-platanin proteins, and the primary function of this protein family has not yet been elucidated. In this study, we investigated the biochemical properties of the cerato-platanin protein EPL1 from T. atroviride. Our results showed that EPL1 readily self-assembles at air/water interfaces and forms protein layers that can be redissolved in water. These properties are reminiscent of hydrophobins, which are amphiphilic fungal proteins that accumulate at interfaces. Atomic force microscopy imaging showed that EPL1 assembles into irregular meshwork-like substructures. Furthermore, surface activity measurements with EPL1 revealed that, in contrast to hydrophobins, EPL1 increases the polarity of aqueous solutions and surfaces. In addition, EPL1 was found to bind to various forms of polymeric chitin. The T. atroviride genome contains three epl genes. epl1 was predominantly expressed during hyphal growth, whereas epl2 was mainly expressed during spore formation, suggesting that the respective proteins are involved in different biological processes. For epl3, no gene expression was detected under most growth conditions. Single and double gene knock-out strains of epl1 and epl2 did not reveal a detectable phenotype, showing that these proteins are not essential for fungal growth and development despite their abundant expression. Background: EPL1 belongs to the cerato-platanin protein family found exclusively in fungi and associated with fungus-host interactions. Results: EPL1 self-assembles at air/water interfaces, increases the polarity of surfaces and solutions, and binds to chitin. Conclusion: The reported properties for EPL1 show that cerato-platanin proteins are clearly different from hydrophobins. Significance: This study reports several novel properties for cerato-platanin proteins.