Peptides, Lipopeptides Used to Fight Bacteria

The first is a "magnetic” weapon--a natural antibiotic produced by all organisms. Because these antimicrobial peptides (AMPs) are positively charged, they are attracted to the bacteria's negatively charged surface similar to a magnet, where they can then exert their antibacterial effects. The second, "detergent-like” weapon, called a lipopeptide, is produced only by bacteria and fungi, which, due to a negative charge, target mainly fungi. This weapon contains a fatty acid chain that, similar to chains in soap that dissolve dirt and oils, breaks down the fatty membranes of the fungi.

In the study, published in the October 12, 2006, issue of the journal Proceedings of the [U.S.] National Academy of Sciences (PNAS), Prof. Yechiel Shai and Ph.D. students Arik Makovitzki and Dorit Avrahami from the biological chemistry department at the Weizmann Institute of Science (Rehovot, Israel) have effectively combined the properties of AMPs with lipopeptides, resulting in a synthetic lipopeptide that has both a positive charge and the soap-like ability to dissolve oils.

By changing the length of the fatty acid chains and the sequence of positively charged amino acids, the investigators were able to create a range of weapons. Some are active against both bacteria and fungi, whereas others target just one or the other. Furthermore, they managed to design these new synthetic peptides (protein fragments) to contain only four amino acids, as opposed to the 12-50 found in their natural forms.

These results will hopefully provide a whole new range of potential applications. The short length of the synthetic peptide makes it appealing for drug design as it would be both easier and economically less expensive to synthesize, less prone to resistance, and potentially engineered to target a large array of bacterial and fungal infections.



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Weizmann Institute of Science