The interfacial properties of the peptide polybia-mp1 and its interaction with DPPC are modulated by lateral electrostatic attractions

D. S. ALVARES; M.L.FANANI; J. RUGGERO NETO; N. WILKE

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 1858

0005-2736

Polybia-MP1 (IDWKKLLDAAKQIL-NH2), extractedfrom the Brazilian wasp Polybia paulista,exhibits a broad-spectrum bactericidal activity without being hemolytic andcytotoxic. In the present study, we analyzed the surface properties of thepeptide and its interaction with DPPC in Langmuir monolayers. Polybia-MP1 formedstable monolayers, with lateral areas and surface potential values suggesting amostly a-helical structure oriented near perpendicular to themembrane plane. In DPPC-peptide mixed monolayers, MP1 co-crystalized with thelipid forming branched domains only when the subphase was pure water. Onsubphases with high salt concentrations or at acidic or basic conditions, thepeptide formed less densely packed films and was excluded from the domains,indicating the presence of attractive electrostatic interactions betweenpeptides, which allow them to get closer to each other and to interact withDPPC probably as a consequence of a particular peptide arrangement. Theresidues responsible of the peptide-peptide attraction are suggested to be theanionic aspartic acids and the cationic lysines, which form a salt bridge,leading to oriented interactions in the crystal and thereby to brancheddomains. For this peptide, the balance between total attractive and repulsive interactionsmay be finely tuned by the aqueous ionic strength and pH, and since this effectis related with lysines and aspartic acids, similar effects may also occur inother peptides containing these residues in their sequences.