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Soluble hydrophobin mutants produced in Escherichia coli can self-assemble at various interfaces

Year: 2020

Journal: J. Colloid Interface Sci., Volume 573, AUG 1, page 384–395

Authors: Cheng, Yingying; Wang, Bin; Wang, Yanyan; Zhang, Huayue; Liu, Cheng; Yang, Lu; Chen, Zhuozhi; Wang, Yinan; Yang, Haitao; Wang, Zefang

Organizations: National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [81601593, 31970048, 61501320]

Keywords: Hydrophobins; Disulfide bridges; Self-assembly; Escherichia coli expression system

Hydrophobins are small, secreted amphiphilic proteins produced by filamentous fungi. Due to their charming ability to self-assemble at different interfaces, several efforts have been made in recent years to produce hydrophobins at a large scale for industrial applications. However, producing soluble and functional hydrophobins in bacterial expression systems is challenging because all hydrophobins contain eight conserved cysteine residues, resulting in the formation of inclusion bodies. Here, two cysteine mutants for both class I and class II hydrophobins were successfully produced in Escherichia coli in soluble form. Subsequent experiments systematically demonstrated that those two mutants preserved the ability to self-assemble at water-water, air-water and oil-water interfaces similarly to native hydrophobins. We also found that disulfide bridges differently influenced the self-assembly of hydrophobins. They were not involved in the self-assembly of the class I hydrophobin HGFI, but directly affected the self-assembly of the class II hydrophobin HFBI. Our study demonstrated that the bacterial expression system was suitable for producing soluble and functional hydrophobin mutants, which have the potential to replace native hydrophobins produced in other complicated production systems. (C) 2020 Elsevier Inc. All rights reserved.