Environmental Conditions Modulate the Switch among Different States of the Hydrophobin Vmh2 from Pleurotus ostreatus

Abstract

Fungal hydrophobins are amphipathic, highly surface-active, and self-assembling proteins. The class I hydrophobin Vmh2 from the basidiomycete fungus Pleurotus ostreatus seems to be the most hydrophobic hydrophobin characterized so far. Structural and functional properties of the protein as a function of the environmental conditions have been determined. At least three distinct phenomena can occur, being modulated by the environmental conditions: (1) when the pH increases or in the presence of Ca(2+) ions, an assembled state, β-sheet rich, is formed; (2) when the solvent polarity increases, the protein shows an increased tendency to reach hydrophobic/hydrophilic interfaces, with no detectable conformational change; and (3) when a reversible conformational change and reversible aggregation occur at high temperature. Modulation of the Vmh2 conformational/aggregation features by changing the environmental conditions can be very useful in view of the potential protein applications.

ATR FT-IR spectroscopy on Vmh2 hydrophobin self-assembled layers for Teflon membrane bio-functionalization

“…It is evident that the ␤-sheet structure is always dominant. It has been previously demonstrated that pH increase by NH 3 addition leads to amyloid-like fibrils formation in Vmh2 solutions [15]. FT-IR deconvolution analysis of B2 and B4 in comparison with B1 and B3 samples, respectively, shows a decrease of ␣-helical, as expected, and an increase of ␤-turn contribution, rather than ␤-sheet, phenomenon usually ascribed to an increase of disorder.…”

“…Since the obtained value for amide content are related to the average on the whole membrane surface analyzed, this result can be due to a more uniform and homogeneous distribution of the protein samples slowly dried at room temperature with respect to that quickly dried at 60 • C. On the other hand, when the pH was increased by adding NH 3 (B2, B4), the obtained values of amide content were very similar, independently from the drying temperature. In this case the layer formation process was mainly triggered by the pH change leading to a quick aggregation, as previously demonstrated [15]. Moreover the B6 samples prepared in 20% ethanol and dried at room temperature are characterized by the highest amide content, the lowest lipid/amide ratio and a carbohydrate/amide ratio with an intermediate value among the ones shown in Table 3.…”

“…Among Class I hydrophobins, a protein extracted from Pleurotus ostreatus, named Vmh2, has been used for bioactive modification of silicon and steel surfaces [12][13][14]. Vmh2 is soluble in solvents less polar than water (i.e., ethanol, at least 40%) [15]. By increasing the solvent polarity, the Vmh2 solubility decreases, although no conformational transition is observed.…”

Hybrid bio/non-bio interfaces for protein-glucose interaction monitoring

“…7 Unfortunately, since the crystalline model of HFB is not yet available, the interaction between protein and sugars is not completely understood: from biological consideration, HFB is not a sugar binding protein, so that the presence of a specific binding site cannot be hypothesized, but it selectively binds glucose with respect to other sugars, 28 at least in solutions. One of the aims of this work is to verify if the selfassembled biolayer of hydrophobins is still able to interact with glucose.…”

Environmental polarity induces conformational transitions in a helical peptide sequence from bacteriophage T4 lysozyme and its tandem duplicate: a molecular dynamics simulation study

“…It is also known that apart from the primary sequence, environmental factors like tertiary contacts within the folded protein, solvent polarity, ions, pH, temperature etc. have also been considered to be of great significance in determining the conformational preference of a sequence [5,6]. Studies have shown that upon decreasing the solvent polarity an α-to 3 10 -helix conformational switching occurs, as in the case of an acylated heptapep tide amide comprising six C α -tetrasubstituted amino acids and one histidine [7] and an amphiphilic peptide of the triacylglycerol lipase derived from Pseudomonas aeruginosa [8].…”