Class I Hydrophobin Vmh2 Adopts Atypical Mechanisms to Self-Assemble into Functional Amyloid Fibrils

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• 作者：Alfredo Maria Gravagnuolo ; Sara Longobardi ; Alessandra Luchini ; Marie-Sousai Appavou ; Luca De Stefano ; Eugenio Notomista ; Luigi Paduano ; Paola Giardina
• 刊名：Biomacromolecules
• 出版年：2016
• 出版时间：March 14, 2016
• 年：2016
• 卷：17
• 期：3
• 页码：954-964
• 全文大小：658K
• ISSN：1526-4602

文摘

Hydrophobins are fungal proteins whose functions are mainly based on their capability to self-assemble into amphiphilic films at hydrophobic–hydrophilic interfaces (HHI). It is widely accepted that class I hydrophobins form amyloid-like structures, named rodlets, which are hundreds of nanometers long, packed into ordered lateral assemblies and do not exhibit an overall helical structure. We studied the self-assembly of the Class I hydrophobin Vmh2 from Pleurotus ostreatus in aqueous solutions by dynamic light scattering (DLS), thioflavin T (ThT), fluorescence assay, circular dichroism (CD), cryogenic trasmission electron microscopy (cryo-TEM), and TEM. Vmh2 does not form fibrillar aggregates at HHI. It exhibits spherical and fibrillar assemblies whose ratio depends on the protein concentration when freshly solubilized at pH ≥ 7. Moreover, it spontaneously self-assembles into isolated, micrometer long, and twisted amyloid fibrils, observed for the first time in fungal hydrophobins. This process is promoted by acidic pH, temperature, and Ca²⁺ ions. A model of self-assembly into amyloid-like structures has been proposed.