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    Structure-Dependent Interfacial Properties of Chaplin F from Streptomyces coelicolor

    Year: 2017

    Journal: Biomolecules, Volume 7, SEP

    Authors: Dokouhaki, Mina; Prime, Emma L.; Hung, Andrew; Qiao, Greg G.; Day, Li; Gras, Sally L.

    Organizations: ARC Dairy Innovation Hub [IH2010005]; ARC Research Hub for Future Fibres [IH140100018]

    Keywords: self-assembly; pressure/area isotherms; circular dichroism; atomic force microscopy; Brewster angle microscopy

    Chaplin F (Chp F) is a secreted surface-active peptide involved in the aerial growth of Streptomyces. While Chp E demonstrates a pH-responsive surface activity, the relationship between Chp F structure, function and the effect of solution pH is unknown. Chp F peptides were found to self-assemble into amyloid fibrils at acidic pH (3.0 or the isoelectric point (pI) of 4.2), with similar to 99% of peptides converted into insoluble fibrils. In contrast, Chp F formed short assemblies containing a mixture of random coil and beta-sheet structure at a basic pH of 10.0, where only 40% of the peptides converted to fibrils. The cysteine residues in Chp F did not appear to play a role in fibril assembly. The interfacial properties of Chp F at the air/water interface were altered by the structures adopted at different pH, with Chp F molecules forming a higher surface-active film at pH 10.0 with a lower area per molecule compared to Chp F fibrils at pH 3.0. These data show that the pH responsiveness of Chp F surface activity is the reverse of that observed for Chp E, which could prove useful in potential applications where surface activity is desired over a wide range of solution pH.
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