Hydrophobin

Hydrophobin
Identifiers
Symbol	Hydrophobin
Pfam	PF01185
InterPro	IPR001338
PROSITE	PDOC00739
SCOP	1r2m
SUPERFAMILY	1r2m
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Fungal hydrophobin
250px Structure of hydrophobin HFBI from Trichoderma reesei
Identifiers
Symbol	Hydrophobin_2
Pfam	PF06766
InterPro	IPR010636
PROSITE	PDOC00739
SCOP	1r2m
SUPERFAMILY	1r2m
OPM protein	1r2m
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Hydrophobins are a group of small (~100 amino acids) cysteine-rich proteins that are expressed only by filamentous fungi. They are known for their ability to form a hydrophobic (water-repellent) coating on the surface of an object. They were first discovered and separated in Schizophyllum commune in 1991. Based on differences in hydropathy patterns and biophysical properties, they can be divided into two categories: class I and class II. Hydrophobins can self-assemble into a monolayer on hydrophobic:hydrophilic interfaces such as a water:air interface. Class I monolayer contains the same core structure as amyloid fibrils, and is positive to Congo red and thioflavin T. The monolayer formed by class I hydrophobins has a highly ordered structure, and can only be dissociated by concentrated trifluoroacetate or formic acid. Monolayer assembly involves large structural rearrangements with respect to the monomer.

Fungi make complex aerial structures and spores even in aqueous environments.

Hydrophobins have been identified in ascomycetes and basidiomycetes; whether they exist in other groups is not known. Hydrophobins are generally found on the outer surface of conidia and of the hyphal wall, and may be involved in mediating contact and communication between the fungus and its environment. Some family members contain multiple copies of the domain.

This family of proteins includes the rodlet proteins of Neurospora crassa (gene eas) and Emericella nidulans (gene rodA), these proteins are the main component of the hydrophobic sheath covering the surface of many fungal spores.

Genomic sequencing of two fungi from dry or salty environments (Wallemia sebi and W. ichthyophaga) revealed that these species contain predicted hydrophobins with unusually high proportion of acidic amino acids and therefore with potentially novel characteristics. High proportion of acidic amino acids is thought to be an adaptation of proteins to high concentrations of salt.

Further reading

This article incorporates text from the public domain Pfam and InterPro IPR001338