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Bioproduction and characterization of a pH responsive self‐assembling peptide
Authors:Jessica M Riley  Amalia Aggeli  Rudolf J Koopmans  Michael J McPherson
Institution:1. Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, School of Chemistry, University of Leeds, Leeds LS2 9JT, UK;2. telephone: +44‐113‐343‐2595;3. fax: +44‐113‐343‐3160;4. Centre for Self‐Organising Molecular Systems, School of Chemistry, University of Leeds, Leeds, UK;5. PU Product R&D, Dow Europe GmbH, Freienbach, Switzerland
Abstract:Peptide P11‐4 (QQRFEWEFEQQ) was designed to self‐assemble to form β‐sheets and nematic gels in the pH range 5–7 at concentrations ≥12.6 mM in water. This self‐assembly is reversibly controlled by adjusting the pH of the solvent. It can also self‐assemble into gels in biological media. This together with its biocompatibility and biodegradability make P11‐4 an attractive building block for the fabrication of nanoscale materials with uses in, for example, tissue engineering. A limitation to large‐scale production of such peptides is the high cost of solid phase chemical synthesis. We describe expression of peptide P11‐4 in the bacterium Escherichia coli from constructs carrying tandem repeats of the peptide coding sequence. The vector pET31b+ was used to express P11‐4 repeats fused to the ketosteroid isomerase protein which accumulates in easily recoverable inclusion bodies. Importantly, the use of auto‐induction growth medium to enhance cell density and protein expression levels resulted in recovery of 2.5 g fusion protein/L culture in both shake flask and batch fermentation. Whole cell detergent lysis allowed recovery of inclusion bodies largely composed of the fusion protein. Cyanogen bromide cleavage followed by reverse phase HPLC allowed purification of the recombinant peptide with a C‐terminal homoserine lactone (rP11‐4(hsl)). This recombinant peptide formed pH dependent hydrogels, displayed β‐structure measured by circular dichroism and fibril formation observed by transmission electron microscopy. Biotechnol. Bioeng. 2009;103: 241–251. © 2009 Wiley Periodicals, Inc.
Keywords:self‐assembling peptide  nanostructured material  recombinant peptide
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