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Structure-function characterization and optimization of a plant-derived antibacterial peptide.

ABSTRACT: Crushed seeds of the Moringa oleifera tree have been used traditionally as natural flocculants to clarify drinking water. We previously showed that one of the seed peptides mediates both the sedimentation of suspended particles such as bacterial cells and a direct bactericidal activity, raising the possibility that the two activities might be related. In this study, the conformational modeling of the peptide was coupled to a functional analysis of synthetic derivatives. This indicated that partly overlapping structural determinants mediate the sedimentation and antibacterial activities. Sedimentation requires a positively charged, glutamine-rich portion of the peptide that aggregates bacterial cells. The bactericidal activity was localized to a sequence prone to form a helix-loop-helix structural motif. Amino acid substitution showed that the bactericidal activity requires hydrophobic proline residues within the protruding loop. Vital dye staining indicated that treatment with peptides containing this motif results in bacterial membrane damage. Assembly of multiple copies of this structural motif into a branched peptide enhanced antibacterial activity, since low concentrations effectively kill bacteria such as Pseudomonas aeruginosa and Streptococcus pyogenes without displaying a toxic effect on human red blood cells. This study thus identifies a synthetic peptide with potent antibacterial activity against specific human pathogens. It also suggests partly distinct molecular mechanisms for each activity. Sedimentation may result from coupled flocculation and coagulation effects, while the bactericidal activity would require bacterial membrane destabilization by a hydrophobic loop.

SUBMITTER: Suarez M

PROVIDER: S-EPMC1195432 | biostudies-literature | 2005 Sep

REPOSITORIES: biostudies-literature

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Structure-function characterization and optimization of a plant-derived antibacterial peptide.

Suarez Mougli M Haenni Marisa M Canarelli Stéphane S Fisch Florian F Chodanowski Pierre P Servis Catherine C Michielin Olivier O Freitag Ruth R Moreillon Philippe P Mermod Nicolas N

Antimicrobial agents and chemotherapy 20050901 9

Crushed seeds of the Moringa oleifera tree have been used traditionally as natural flocculants to clarify drinking water. We previously showed that one of the seed peptides mediates both the sedimentation of suspended particles such as bacterial cells and a direct bactericidal activity, raising the possibility that the two activities might be related. In this study, the conformational modeling of the peptide was coupled to a functional analysis of synthetic derivatives. This indicated that partl ...[more]

PMID: 16127062

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Project description:Multiple new approaches to tackle multidrug resistant infections are urgently needed and under evaluation. One nanotechnology-based approach to delivering new relevant therapeutics involves silicon accumulator plants serving as a viable silicon source in green routes for the fabrication of the nanoscale drug delivery carrier porous silicon (pSi). If the selected plant leaf components contain medicinally-active species as well, then a single substance can provide not only the nanoscale high surface area drug delivery carrier, but the drug itself. With this idea in mind, porous silicon was fabricated from joints of the silicon accumulator plant Bambuseae (Tabasheer) and loaded with an antibacterial extract originating from leaves of the same type of plant (Bambuseae arundinacea). Preparation of porous silicon from Tabasheer includes extraction of biogenic silica from the ground plant by calcination, followed by reduction with magnesium in the presence of sodium chloride, thereby acting as a thermal moderator that helps to retain the mesoporous structure of the feedstock. The purified product was characterized by a combination of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and low temperature nitrogen gas adsorption measurements. Antimicrobial activity and minimum inhibitory concentration of a leaf extract of Bambuseae arundinacea was tested against the bacteria Escherichia Coli (E. Coli) and Staphylococcus aureus (S. Aureus), along with the fungus Candida albicans (C. Albicans). A S. aureus active ethanolic leaf extract was loaded into the above Tabasheer-derived porous silicon. Initial studies indicate sustained in vitro antibacterial activity of the extract-loaded plant derived pSi (25 wt %, TGA), as measured by disk diffusion inhibitory zone assays. Subsequent chromatographic separation of this extract revealed that the active antimicrobial species present include stigmasterol and 2,6-dimethoxy-p-benzoquinone.

Dataset Information

Structure-function characterization and optimization of a plant-derived antibacterial peptide.

Publications

Structure-function characterization and optimization of a plant-derived antibacterial peptide.

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