Composition and antimicrobial activity of the skin peptidome of Russian brown frog Rana temporaria.

A nano-HPLC-ESI-OrbiTrap study involving HCD and ETD spectra has been carried out to clarify the composition of the skin peptidome of brown Russian frogs Rana temporaria. This approach allowed determinantion of 76 individual peptides, increasing 3-fold the identified portion of the peptidome in comparison to that obtained earlier with FTICR MS. A search for the new bradykinin related peptides (BRPs) was carried out by reconstructing mass chromatograms based on the ion current of characteristic b- and y-ions. Several peptides were reported in the secretion of R. temporaria for the first time. The overall antibacterial activity of the skin secretion in general and of one individual peptide (Brevinin 1Tb) was determined using PMEU Spectrion (Portable Microbe Enrichment Unit) technology. The inhibitory effects of these peptides on Staphylococcus aureus and Salmonella enterica Serovar typhimutium were equal in scale to that reported for some antibiotics.

Identification of a common structural motif in the disordered N-terminal region of bacterial flagellins--evidence for a new class of fibril-forming peptides.

Flagellin proteins lacking the N- or C-terminus form polymers of reduced filament stability and straight morphology, in contrast to the coiled native flagella. In the present study, the N-terminal amino acid sequence of flagellins of the anaerobic beer spoilage bacteria Pectinatus cerevisiiphilus and Pectinatus frisingiensis as well as Enterobacter aerogenes and Pseudomonas sp. were determined. Sequence similarity was revealed between these and the N-termini of all known eubacterial flagellins. Synthetic peptides corresponding to the first 15 amino acid residues of the flagellins of Pectinatus, Campylobacter jejuni, E. aerogenes or Proteus mirabilis flagellins had a spontaneous tendency under physiological conditions to form 4-6 nm broad, 1-2 microm long fibrillar structures that had a tendency to form clusters. In contrast, the Pectinatus peptide missing residues 1-3 did not form fibrils. The peptide missing residues 13-15 formed fibrils less easily, and the peptide missing residues 11-15 formed fibrils almost without clustering. In electron micrographs, the fibrillisation of the bacterial flagellar peptides resembled that of beta-amyloid and prion peptides. 1H-NMR and infrared spectroscopy studies with homology analysis indicate that although the flagellar N-terminal peptides are flexible with many conformational minima, they have a significant tendency to form beta-type structures and a loop in the middle of the peptide. The hydrophobic character of the N-terminus together with the property of forming a conserved beta-strand-loop-beta-strand motif may be related to a mechanism involved in attaining the proper morphology and stability of the flagellar filament, by providing a device for facilitating the attachment of the flagellin monomers to each other. The flagellar peptides represent a new class of fibril-forming peptides.