Structure-activity study of the antibacterial peptide fallaxin

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Sandra Lerche Søndergaard, Niels Frimodt-Møller, Birthe Brandt Kragelund, Paul Robert Hansen

Fallaxin is a 25-mer antibacterial peptide amide, which was recently isolated from the West Indian mountain chicken frog Leptodactylus fallax. Fallaxin has been shown to inhibit the growth of several Gram-negative bacteria including Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Here, we report a structure-activity study of fallaxin based on 65 analogs, including a complete alanine scan and a full set of N- and C-terminal truncated analogs. The fallaxin analogs were tested for hemolytic activity and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate resistant S. aureus, (VISA), methicillin-susceptible S. aureus (MSSA), E. coli, K. pneumoniae, and P. aeruginosa. We identified several analogs, which showed improved antibacterial activity compared to fallaxin. Our best candidate was FA12, which displayed MIC values of 3.12, 25, 25, and 50 µM against E. coli, K. pneumoniae, MSSA, and VISA, respectively. Furthermore, we correlated the antibacterial activity with various structural parameters such as charge, hydrophobicity <H>, mean hydrophobic moment <µH>, and {alpha}-helicity. We were able to group the active and inactive analogs according to mean hydrophobicity <H> and mean hydrophobic moment <µH>. Far-UV CD-spectroscopy experiments on fallaxin and several analogs in buffer, in TFE, and in membrane mimetic environments (small unilamellar vesicles) indicated that a coiled-coil conformation could be an important structural trait for antibacterial activity. This study provides data that support fallaxin analogs as promising lead structures in the development of new antibacterial agents.
Original languageEnglish
JournalProtein Science
Volume16
Issue number9
Pages (from-to)1969-1976
Number of pages8
ISSN0961-8368
DOIs
Publication statusPublished - 2007

    Research areas

  • LIFE - alanine scan, antibacterial activity, coiled-coil conformation, fallaxin, solid-phase peptide synthesis

ID: 8079246