Cationic antimicrobial peptides features

Despite the variety of different sources, sequences and structures, all cationic antimicrobial peptides share some common features small size (12-50 amino acids), positive net charge (+2 to +9), amphiphilic (>30% hydrophobic amino acids) and antimicrobial and/or immunomodulatory activity. Some cationic antimicrobial peptides also show antiviral (14) and/or anticancer activity (15) as well as wound healing properties (16). More than 1000... 

Defensins, potent antimicrobial and proin-flammatory peptides antimicrobial peptides). Mammalian defensins are cationic peptides (Mr 3.5. 5 kDa), rich in lysine and arginine containing six cysteine residues which form three characteristic disulfide bridges. According to the alignment of the disulfide bonds and the overall structure, defensins can be divided into three groups a-defensins, /S-defensins, and 0-defensins. Antimicrobial peptides of plants or insects have also been termed defensins, though they have different structural features in comparison to vertebrate defensins. a-Defensins consist of... 

We have already described that a number of rhizobial LPS mutants are sym-biotically defective because they likely induce an increased defense response by the host and/or are more sensitive to the host defense response. One structural feature of rhizobial LPS that appears to be important is the presence of OPS since its absence appears to result in a more robust plant defense response. We have also suggested (above) that the lack of OPS exposes the anionic COS on the bacterial surface which may make the rhizobial cell more sensitive to antimicrobial cationic peptides. Recent work in our laboratory (Brown, unpublished) has shown that a mutation of R. leguminosarum biovar viciae 3841 which specifically results in the loss of GalA residues from the core increases resistance to cationic peptides. It has also recently been shown that R. etli CE3 mutants in IpxE and IpxF, which are unable to remove the 1 and 4 -phosphates and, therefore have LA with increased anionic character, show increased sensitivity to cationic peptides (Ingram et al., 2010). 

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