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Interfacial self-assembly of a bacterial hydrophobin.

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 ?-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.

SUBMITTER: Bromley KM

PROVIDER: S-EPMC4418867 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Interfacial self-assembly of a bacterial hydrophobin.

Bromley Keith M KM Morris Ryan J RJ Hobley Laura L Brandani Giovanni G Gillespie Rachel M C RM McCluskey Matthew M Zachariae Ulrich U Marenduzzo Davide D Stanley-Wall Nicola R NR MacPhee Cait E CE

Proceedings of the National Academy of Sciences of the United States of America 20150413 17

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 p ...[more]

PMID: 25870300

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Project description:BackgroundProtocell refers to the basic unit of life and synthetic molecular assembly with cell structure and function. The protocells have great applications in the field of biomedical technology. Simulating the morphology and function of cells is the key to the preparation of protocells. However, some organic solvents used in the preparation process of protocells would damage the function of the bioactive substance. Perfluorocarbon, which has no toxic effect on bioactive substances, is an ideal solvent for protocell preparation. However, perfluorocarbon cannot be emulsified with water because of its inertia.MethodsSpheroids can be formed in nature even without emulsification, since liquid can reshape the morphology of the solid phase through the scouring action, even if there is no stable interface between the two phases. Inspired by the formation of natural spheroids such as pebbles, we developed non-interfacial self-assembly (NISA) of microdroplets as a step toward synthetic protocells, in which the inert perfluorocarbon was utilized to reshape the hydrogel through the scouring action.ResultsThe synthetic protocells were successfully obtained by using NISA-based protocell techniques, with the morphology very similar to native cells. Then we simulated the cell transcription process in the synthetic protocell and used the protocell as an mRNA carrier to transfect 293T cells. The results showed that protocells delivered mRNAs, and successfully expressed proteins in 293T cells. Further, we used the NISA method to fabricate an artificial cell by extracting and reassembling the membrane, proteins, and genomes of ovarian cancer cells. The results showed that the recombination of tumor cells was successfully achieved with similar morphology as tumor cells. In addition, the synthetic protocell prepared by the NISA method was used to reverse cancer chemoresistance by restoring cellular calcium homeostasis, which verified the application value of the synthetic protocell as a drug carrier.ConclusionThis synthetic protocell fabricated by the NISA method simulates the occurrence and development process of primitive life, which has great potential application value in mRNA vaccine, cancer immunotherapy, and drug delivery.

Dataset Information

Interfacial self-assembly of a bacterial hydrophobin.

Publications

Interfacial self-assembly of a bacterial hydrophobin.

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