title: 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.
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.
authors.affiliation: USP, University of São Paulo, Department of Physiology and Biophysics, Biomedical Sciences Institute, São Paulo, SP, Brazil. cabrera.marcia@gmail.com
authors.forename: Marcia Perez
authors.initials: MP
authors.lastname: Dos Santos Cabrera
authors.forename: Manoel
authors.initials: M
authors.lastname: Arcisio-Miranda
authors.forename: Sabrina Thais
authors.initials: ST
authors.lastname: Broggio Costa
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Konno
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Ruggiero
authors.forename: Joaquim
authors.initials: J
authors.lastname: Procopio
authors.forename: João
authors.initials: J
authors.lastname: Ruggiero Neto
mesh_terms: D000577:Amides / Q000737:chemistry*; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D002942:Circular Dichroism; D008051:Lipid Bilayers; D014862:Wasp Venoms / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000577:Amides; D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D014862:Wasp Venoms; C443041:anoplin