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

D. DOS SANTOS ALVARES, M.L. FANANI, N. WILKE, J. RUGGIERO NETO.

Pueryo Iguazu

Congreso; 56th International Conference on the Bioscience of lipids; 2015

Polybia-MP1 (IDWKKLLDAAKQIL-NH2), extracted from the Brazilian wasp Polybia paulista, exhibits a broadspectrumbactericidal activity without being hemolytic and cytotoxic. In the present study, we analyzed the surfaceproperties of the peptide and its interactionwith DPPC in Langmuir monolayers. Polybia-MP1 formed stablemonolayers, with lateral areas and surface potential values suggesting a mostly α-helical structure oriented nearperpendicular to the membrane plane. In DPPC?peptide mixed monolayers, MP1 co-crystallized with the lipidforming branched domains only when the subphasewas purewater. On subphaseswith high salt concentrationsor at acidic or basic conditions, the peptide formed less densely packed films andwas excluded fromthe domains,indicating the presence of attractive electrostatic interactions between peptides, which allow them to get closerto each other and to interact with DPPC probably as a consequence of a particular peptide arrangement. The residuesresponsible of the peptide?peptide attraction are suggested to be the anionic aspartic acids and the cationiclysines,which form a salt bridge, leading to oriented interactions in the crystal and thereby to branched domains.For this peptide, the balance between total attractive and repulsive interactions may be finely tuned by the aqueousionic strength and pH, and since this effect is related with lysines and aspartic acids, similar effects may alsooccur in other peptides containing these residues in their sequences.