Hydrophobins from Aspergillus species cannot be clearly divided into two classes

Abstract

BackgroundHydrophobins are a family of small secreted proteins with a characteristic pattern of eight cysteine residues found exclusively in filamentous fungi. They have originally been divided into two classes based on their physical properties and hydropathy patterns, and are involved in the attachment of hyphae to hydrophobic structures, the formation of aerial structures and appear to be involved in pathogenicity.FindingsAnalysis of nine genome sequences from seven Aspergilli revealed fifty hydrophobins, where each species displayed between two to eight hydrophobins. Twenty of the identified hydrophobins have not previously been described from these species. Apart from the cysteines, very little amino acid sequence homology was observed. Twenty-three of the identified hydrophobins could be classified as class I hydrophobins based on their conserved cysteine spacing pattern and hydropathy pattern. However twenty-six of the identified hydrophobins were intermediate forms. Notably, a single hydrophobin, ATEG_04730, from Aspergillus terreus displayed class II cysteine spacing and had a class II hydropathy pattern.ConclusionFifty hydrophobins were identified in Aspergillus, all containing the characteristic eight cysteine pattern. Aspergillus terreus exhibited both class I and class II hydrophobins. This is the first report of an Aspergillus species with the potential to express both class I and class II hydrophobins. Many of the identified hydrophobins could not directly be allocated to either class I or class II.

Hydrophobin genes of the entomopathogenic fungus, Metarhizium brunneum, are differentially expressed and corresponding mutants are decreased in virulence

“…All other hyd mutants in this study retained surface hydrophobicity, suggesting that there may be some overlapping functionality of these genes or other genes yet unidentiWed in the genome. In this regard, two recent genomic searches have identiWed a number of hydrophobin and hydrophobin-like genes in Aspergillus (Jensen et al 2010) and Trichoderma species (Seidl-Seiboth et al 2011), of which many cannot easily be categorized into class I and II types, and they form distinct clades separate from known fungal sequences with as yet unknown functions.…”

“…Hydrophobins have typically been divided into two major classes (I and II) based on their hydropathy patterns and solubility characteristics (Wösten 2001), although more recent studies indicate that there may be other classes of fungal hydrophobin and hydrophobin-like genes (Jensen et al 2010;Seidl-Seiboth et al 2011). Class I members share physiological similarity in that they form aggregates that are highly insoluble in aqueous solution, whereas class II members form aggregates that dissolve more easily (Linder et al 2005).…”

Two Novel Class II Hydrophobins from Trichoderma spp. Stimulate Enzymatic Hydrolysis of Poly(Ethylene Terephthalate) when Expressed as Fusion Proteins

“…These amphiphilic properties have consequently raised considerable industrial interest in their application for the modification of surfaces and biopolymers (39)(40)(41)(42). However, the diversity of HFBs has thus far not been taken into account: based on their solubility in solvents, hydropathy profiles and spacing between the conserved cysteines hydrophobins are traditionally grouped into class I and class II, respectively (15,16,36,43), although it has recently been shown that this classification is more complex (32,44), and there may instead be a continuum of species-specific classes. Askolin et al (45) have shown that the properties of the class II hydrophobins HFB1 and HFB2 of T. reesei clearly differ from those reported for class I hydrophobins by forming less-stable membranes at a hydrophilichydrophobic interface and by not showing a change in secondary structure and ultrastructure at the water-air interface.…”

Aspergillus Cell Wall and Biofilm

“…Sequence analyses indicated that all except RodDp and RodEp belong to class I; RodDp, RodEp and RodGp are of intermediate forms [6]. Only RodAp is isolated and well studied, whereas the roles of the other hydrophobins (RodBp to RodGp) in A. fumigatus are unknown and thus currently a focus of our laboratory.…”