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Surface-water Interface Induces Conformational Changes Critical for Protein Adsorption: Implications for Monolayer Formation of EAS Hydrophobin.

Ley K, Christofferson A, Penna M, Winkler D, Maclaughlin S, Yarovsky I - Front Mol Biosci (2015)

Bottom Line: The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth.Specific and water mediated interactions with the surface were also analyzed.We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution.

View Article: PubMed Central - PubMed

Affiliation: Health Innovations Research Institute and School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University Melbourne, VIC, Australia.

ABSTRACT
The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth. These proteins have attracted increasing attention for industrial and biomedical applications, with the aim of designing surfaces that have the potential to maintain their clean state by resisting non-specific protein binding. To gain a better understanding of this process, we have employed all-atom molecular dynamics to study initial stages of the spontaneous adsorption of monomeric EAS hydrophobin on fully hydroxylated silica, a commonly used industrial and biomedical substrate. Particular interest has been paid to the Cys3-Cys4 loop, which has been shown to exhibit disruptive behavior in solution, and the Cys7-Cys8 loop, which is believed to be involved in the aggregation of EAS hydrophobin at interfaces. Specific and water mediated interactions with the surface were also analyzed. We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution. We have also identified intermittent interactions with water which mediate the protein adsorption to the surface, as well as longer lasting interactions which control the diffusion of water around the adsorption site. These results have shown that EAS behaves in a similar way at the air-water and surface-water interfaces, and have also highlighted the need for hydrophilic ligand functionalization of the silica surface in order to prevent the adsorption of EAS hydrophobin.

No MeSH data available.


Distance between the center of mass of residues and the average height of the surface hydroxyl groups for systems that adsorbed (A) through the Cys3-Cys4 loop (Residues 19 to 45, Binding Motif 1) and (B) with the Cys3-Cys4 loop in bulk water (Binding Motif 2). (C) Distance between the center of mass and the average profile of the air-water interface. Different colors represent the initial protein orientation as shown in Figure 1. In Binding Motif 1, black and green colors were from orientation (A), red from orientation (D). In Binding Motif 2, red was from orientation (D) again, and black was from orientation (C).
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Figure 2: Distance between the center of mass of residues and the average height of the surface hydroxyl groups for systems that adsorbed (A) through the Cys3-Cys4 loop (Residues 19 to 45, Binding Motif 1) and (B) with the Cys3-Cys4 loop in bulk water (Binding Motif 2). (C) Distance between the center of mass and the average profile of the air-water interface. Different colors represent the initial protein orientation as shown in Figure 1. In Binding Motif 1, black and green colors were from orientation (A), red from orientation (D). In Binding Motif 2, red was from orientation (D) again, and black was from orientation (C).

Mentions: Hydrophobin adsorption at the surface-water interface occurred spontaneously and we were able to identify two possible binding motifs at the interface, one in which adsorption occurs through the Cys3-Cys4 loop (Binding Motif 1, Figures 2A, 4B), and another which has the Cys3-Cys4 loop away from the surface (Binding Motif 2, Figures 2B, 4C). Interestingly, the initial protein orientation had minimal impact on the binding motif at the surface-water interface, as most systems experienced a slight reorientation in bulk water prior to adsorbing. The exception to this is the system that initially had the Cys3-Cys4 loop closest to the surface (Figure 1B), where the protein segregated to the air-water interface. This is most likely due to the Cys3-Cys4 loop initially contracting toward the β-core of the protein, resulting in increased distance between the protein and surface and therefore minimizing the attractive long-range interactions between them.


Surface-water Interface Induces Conformational Changes Critical for Protein Adsorption: Implications for Monolayer Formation of EAS Hydrophobin.

Ley K, Christofferson A, Penna M, Winkler D, Maclaughlin S, Yarovsky I - Front Mol Biosci (2015)

Distance between the center of mass of residues and the average height of the surface hydroxyl groups for systems that adsorbed (A) through the Cys3-Cys4 loop (Residues 19 to 45, Binding Motif 1) and (B) with the Cys3-Cys4 loop in bulk water (Binding Motif 2). (C) Distance between the center of mass and the average profile of the air-water interface. Different colors represent the initial protein orientation as shown in Figure 1. In Binding Motif 1, black and green colors were from orientation (A), red from orientation (D). In Binding Motif 2, red was from orientation (D) again, and black was from orientation (C).
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Figure 2: Distance between the center of mass of residues and the average height of the surface hydroxyl groups for systems that adsorbed (A) through the Cys3-Cys4 loop (Residues 19 to 45, Binding Motif 1) and (B) with the Cys3-Cys4 loop in bulk water (Binding Motif 2). (C) Distance between the center of mass and the average profile of the air-water interface. Different colors represent the initial protein orientation as shown in Figure 1. In Binding Motif 1, black and green colors were from orientation (A), red from orientation (D). In Binding Motif 2, red was from orientation (D) again, and black was from orientation (C).
Mentions: Hydrophobin adsorption at the surface-water interface occurred spontaneously and we were able to identify two possible binding motifs at the interface, one in which adsorption occurs through the Cys3-Cys4 loop (Binding Motif 1, Figures 2A, 4B), and another which has the Cys3-Cys4 loop away from the surface (Binding Motif 2, Figures 2B, 4C). Interestingly, the initial protein orientation had minimal impact on the binding motif at the surface-water interface, as most systems experienced a slight reorientation in bulk water prior to adsorbing. The exception to this is the system that initially had the Cys3-Cys4 loop closest to the surface (Figure 1B), where the protein segregated to the air-water interface. This is most likely due to the Cys3-Cys4 loop initially contracting toward the β-core of the protein, resulting in increased distance between the protein and surface and therefore minimizing the attractive long-range interactions between them.

Bottom Line: The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth.Specific and water mediated interactions with the surface were also analyzed.We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution.

View Article: PubMed Central - PubMed

Affiliation: Health Innovations Research Institute and School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University Melbourne, VIC, Australia.

ABSTRACT
The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth. These proteins have attracted increasing attention for industrial and biomedical applications, with the aim of designing surfaces that have the potential to maintain their clean state by resisting non-specific protein binding. To gain a better understanding of this process, we have employed all-atom molecular dynamics to study initial stages of the spontaneous adsorption of monomeric EAS hydrophobin on fully hydroxylated silica, a commonly used industrial and biomedical substrate. Particular interest has been paid to the Cys3-Cys4 loop, which has been shown to exhibit disruptive behavior in solution, and the Cys7-Cys8 loop, which is believed to be involved in the aggregation of EAS hydrophobin at interfaces. Specific and water mediated interactions with the surface were also analyzed. We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution. We have also identified intermittent interactions with water which mediate the protein adsorption to the surface, as well as longer lasting interactions which control the diffusion of water around the adsorption site. These results have shown that EAS behaves in a similar way at the air-water and surface-water interfaces, and have also highlighted the need for hydrophilic ligand functionalization of the silica surface in order to prevent the adsorption of EAS hydrophobin.

No MeSH data available.