Article

Study of the mechanism of action of anoplin, a helical antimicrobial decapeptide with ion channel-like activity, and the role of the amidated C-terminus.

USP, University of São Paulo, Department of Physiology and Biophysics, Biomedical Sciences Institute, São Paulo, SP, Brazil.
Journal of Peptide Science (impact factor: 1.8). 07/2008; 14(6):661-9. DOI:10.1002/psc.960 pp.661-9
Source: PubMed

ABSTRACT Anoplin, an antimicrobial, helical decapeptide from wasp venom, looses its biological activities by mere deamidation of its C-terminus. Secondary structure determination, by circular dichroism spectroscopy in amphipathic environments, and lytic activity in zwitterionic and anionic vesicles showed quite similar results for the amidated and the carboxylated forms of the peptide. The deamidation of the C-terminus introduced a negative charge at an all-positive charged peptide, causing a loss of amphipathicity, as indicated by molecular dynamics simulations in TFE/water mixtures and this subtle modification in a peptide's primary structure disturbed the interaction with bilayers and biological membranes. Although being poorly lytic, the amidated form, but not the carboxylated, presented ion channel-like activity on anionic bilayers with a well-defined conductance step; at approximately the same concentration it showed antimicrobial activity. The pores remain open at trans-negative potentials, preferentially conducting cations, and this situation is equivalent to the interaction of the peptide with bacterial membranes that also maintain a high negative potential inside.

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Keywords

amidated form
 
amphipathic environments
 
anionic bilayers
 
antimicrobial activity
 
bacterial membranes
 
biological activities
 
biological membranes
 
carboxylated forms
 
circular dichroism spectroscopy
 
helical decapeptide
 
ion channel-like activity
 
lytic activity
 
mere deamidation
 
molecular dynamics simulations
 
negative charge
 
peptide's primary structure
 
Secondary structure determination
 
subtle modification
 
TFE/water mixtures
 
well-defined conductance step