Cationic peptides cecropin

The cationic peptides possess two predominant themes either a hydrophobic core (often helical) with an adjacent cluster of Lys and Arg residues (e.g., melittin and cecropins) or an amphipathic helix with basic side chains aligned along one helical face (e.g., magainins and the S4 segment of the sodium channel). The basic residues promote association with the acidic... 

Upon infection, insects can produce a wide range of antimicrobial peptides, which are synthe zed in the fax. body and/or haemocytes and secreted into the haemolymi. Such peptides include ceert ins (33), and defensin-like peptides such as sapecin and phormicin (34,35). Cecropins are highly amphipathic peptides containing 31-39 residues that form voltage-dependent channels in lipid membranes (36). They were initially isolated from the silk moth Hyolop/tora cecropia (37) and have subsequently been isolated from the flesh fly (sarcoroxin 1) and Drosophila (38,39). Cecropins are distinct from other insect cationic peptides in that they contain no cysteine residues and fail to lyse eukaryotic cells (33),... 

CP-29 is a cecropin/mellitin hybrid cationic peptide (Hancock, Gough, and Fanner, unpublished data). cationic peptide (Falla, T., Hancock, R. E. W., unpublished dau). 

Defensins are variably cationic, relatively arginine-rich, nonglycosylated peptides comprised of 29-34 amino acid residues. Human (HNP-1) and rabbit (NP-5) defensins have been studied by NMR techniques and showed that they are rich in beta sheet structure. Although both types of defensins permeabilize the outer membrane of E. coli [31], they differ from other peptides with similar action but rich in alpha helices such as magainin, mellitin and cecropin. 

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