Interfacial self-assembly of a bacterial hydrophobin

Keith M. Bromley, Ryan J. Morris, Laura Hobley, Giovanni Brandani, Rachel M. C. Gillespie, Matthew McCluskey, Ulrich Zachariae, Davide Marenduzzo, Nicola R. Stanley-Wall, Cait E. MacPhee

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

The majority of bacteria in the natural environment live within the confines of a biofilm. The Gram-positive bacterium Bacillus subtilis forms biofilms that exhibit a characteristic wrinkled morphology and a highly hydrophobic surface. A critical component in generating these properties is the protein BslA, which forms a coat across the surface of the sessile community. We recently reported the structure of BslA, and noted the presence of a large surface-exposed hydrophobic patch. Such surface patches are also observed in the class of surface-active proteins known as hydrophobins, and are thought to mediate their interfacial activity. However, although functionally related to the hydrophobins, BslA shares no sequence nor structural similarity, and here we show that the mechanism of action is also distinct. Specifically, our results suggest that the amino acids making up the large, surface-exposed hydrophobic cap in the crystal structure are shielded in aqueous solution by adopting a random coil conformation, enabling the protein to be soluble and monomeric. At an interface, these cap residues refold, inserting the hydrophobic side chains into the air or oil phase and forming a three-stranded β-sheet. This form then self-assembles into a well-ordered 2D rectangular lattice that stabilizes the interface. By replacing a hydrophobic leucine in the center of the cap with a positively charged lysine, we changed the energetics of adsorption and disrupted the formation of the 2D lattice. This limited structural metamorphosis represents a previously unidentified environmentally responsive mechanism for interfacial stabilization by proteins.

Original languageEnglish
Pages (from-to)5419-5424
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number17
DOIs
Publication statusPublished - 28 Apr 2015

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Biofilms
Protein Conformation
Gram-Positive Bacteria
Bacillus subtilis
Leucine
Adsorption
Lysine
Oils
Membrane Proteins
Proteins
Air
Bacteria
Amino Acids

Cite this

Bromley, K. M., Morris, R. J., Hobley, L., Brandani, G., Gillespie, R. M. C., McCluskey, M., ... MacPhee, C. E. (2015). Interfacial self-assembly of a bacterial hydrophobin. Proceedings of the National Academy of Sciences of the United States of America, 112(17), 5419-5424. https://doi.org/10.1073/pnas.1419016112
Bromley, Keith M. ; Morris, Ryan J. ; Hobley, Laura ; Brandani, Giovanni ; Gillespie, Rachel M. C. ; McCluskey, Matthew ; Zachariae, Ulrich ; Marenduzzo, Davide ; Stanley-Wall, Nicola R. ; MacPhee, Cait E. / Interfacial self-assembly of a bacterial hydrophobin. In: Proceedings of the National Academy of Sciences of the United States of America. 2015 ; Vol. 112, No. 17. pp. 5419-5424.
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Bromley, KM, Morris, RJ, Hobley, L, Brandani, G, Gillespie, RMC, McCluskey, M, Zachariae, U, Marenduzzo, D, Stanley-Wall, NR & MacPhee, CE 2015, 'Interfacial self-assembly of a bacterial hydrophobin', Proceedings of the National Academy of Sciences of the United States of America, vol. 112, no. 17, pp. 5419-5424. https://doi.org/10.1073/pnas.1419016112

Interfacial self-assembly of a bacterial hydrophobin. / Bromley, Keith M.; Morris, Ryan J.; Hobley, Laura; Brandani, Giovanni; Gillespie, Rachel M. C.; McCluskey, Matthew; Zachariae, Ulrich; Marenduzzo, Davide; Stanley-Wall, Nicola R.; MacPhee, Cait E.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 112, No. 17, 28.04.2015, p. 5419-5424.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Interfacial self-assembly of a bacterial hydrophobin

AU - Bromley, Keith M.

AU - Morris, Ryan J.

AU - Hobley, Laura

AU - Brandani, Giovanni

AU - Gillespie, Rachel M. C.

AU - McCluskey, Matthew

AU - Zachariae, Ulrich

AU - Marenduzzo, Davide

AU - Stanley-Wall, Nicola R.

AU - MacPhee, Cait E.

PY - 2015/4/28

Y1 - 2015/4/28

N2 - The majority of bacteria in the natural environment live within the confines of a biofilm. The Gram-positive bacterium Bacillus subtilis forms biofilms that exhibit a characteristic wrinkled morphology and a highly hydrophobic surface. A critical component in generating these properties is the protein BslA, which forms a coat across the surface of the sessile community. We recently reported the structure of BslA, and noted the presence of a large surface-exposed hydrophobic patch. Such surface patches are also observed in the class of surface-active proteins known as hydrophobins, and are thought to mediate their interfacial activity. However, although functionally related to the hydrophobins, BslA shares no sequence nor structural similarity, and here we show that the mechanism of action is also distinct. Specifically, our results suggest that the amino acids making up the large, surface-exposed hydrophobic cap in the crystal structure are shielded in aqueous solution by adopting a random coil conformation, enabling the protein to be soluble and monomeric. At an interface, these cap residues refold, inserting the hydrophobic side chains into the air or oil phase and forming a three-stranded β-sheet. This form then self-assembles into a well-ordered 2D rectangular lattice that stabilizes the interface. By replacing a hydrophobic leucine in the center of the cap with a positively charged lysine, we changed the energetics of adsorption and disrupted the formation of the 2D lattice. This limited structural metamorphosis represents a previously unidentified environmentally responsive mechanism for interfacial stabilization by proteins.

AB - The majority of bacteria in the natural environment live within the confines of a biofilm. The Gram-positive bacterium Bacillus subtilis forms biofilms that exhibit a characteristic wrinkled morphology and a highly hydrophobic surface. A critical component in generating these properties is the protein BslA, which forms a coat across the surface of the sessile community. We recently reported the structure of BslA, and noted the presence of a large surface-exposed hydrophobic patch. Such surface patches are also observed in the class of surface-active proteins known as hydrophobins, and are thought to mediate their interfacial activity. However, although functionally related to the hydrophobins, BslA shares no sequence nor structural similarity, and here we show that the mechanism of action is also distinct. Specifically, our results suggest that the amino acids making up the large, surface-exposed hydrophobic cap in the crystal structure are shielded in aqueous solution by adopting a random coil conformation, enabling the protein to be soluble and monomeric. At an interface, these cap residues refold, inserting the hydrophobic side chains into the air or oil phase and forming a three-stranded β-sheet. This form then self-assembles into a well-ordered 2D rectangular lattice that stabilizes the interface. By replacing a hydrophobic leucine in the center of the cap with a positively charged lysine, we changed the energetics of adsorption and disrupted the formation of the 2D lattice. This limited structural metamorphosis represents a previously unidentified environmentally responsive mechanism for interfacial stabilization by proteins.

U2 - 10.1073/pnas.1419016112

DO - 10.1073/pnas.1419016112

M3 - Article

C2 - 25870300

VL - 112

SP - 5419

EP - 5424

JO - Proceedings of the National Academy of Sciences

JF - Proceedings of the National Academy of Sciences

SN - 0027-8424

IS - 17

ER -

Bromley KM, Morris RJ, Hobley L, Brandani G, Gillespie RMC, McCluskey M et al. Interfacial self-assembly of a bacterial hydrophobin. Proceedings of the National Academy of Sciences of the United States of America. 2015 Apr 28;112(17):5419-5424. https://doi.org/10.1073/pnas.1419016112