Fungal Fibrils: Application of the Amyloid Polymer Structure by Fungi - The Functional Fold: Amyloid Structures in Nature - page 44

3.5 Structural Change During Rodlet Formation

The three-dimensional structures of the monomeric, unassembled
forms of two Class II and one Class I hydrophobins have been
determined. The structures of the two highly homologous Class II
hydrophobins from

Trichoderma reesei , HFBI and HFBII, have been

determined by X-ray crystallography.

40-43

The solution structure of

EAS, the Class I hydrophobin, from N. crassa has been determined by

35

triple-resonance NMR methods. Remarkably, given the low levels

of sequence similarity between the two classes of hydrophobins
and the fact that the assemblies formed by these hydrophobins
are different in morphology and stability, EAS and the HFBI/II
have the same basic topology in the unassembled, monomeric
form (Fig. 3.6a-c). This fold is unique to the hydrophobin family of
proteins. The structures of HFBI and HFBII consist of a core

β

-barrel

β α

comprised of two adjoining -hairpins, with an -helix linked to the

a b

c d

Figure 3.6 The three-dimensional structures of a Class I and a Class II

hydrophobin. (a) Ribbon diagrams of the Class I hydrophobin
EAS (PDB code 2FMC) and (b) the Class II hydrophobin HFBII
(PDB code 1R2M). Cysteine side-chains are shown in yellow.
(c) A superposition of EAS (cyan) and HFBII (pink) showing
the -barrel core is highly similar. (d) Electrostatic surface of

EAS. Negatively and positively charged residues are illustrated
in red and blue, respectively. The charges can be seen to
cluster on a single face of the structure, while the diametrically
opposing face is hydrophobic. See also Colour Insert.

β