title: Interaction of the antimicrobial peptide gomesin with model membranes: a calorimetric study.
abstract: Gomesin is a potent cationic antimicrobial peptide (z = +6) isolated from the Brazilian spider Acanthoscurria gomesiana . The interaction of gomesin with large unilamellar vesicles composed of a 1:1 mixture of zwitterionic (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and anionic (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) phospholipids is studied with isothermal titration calorimetry (ITC). In parallel, light scattering and optical microscopy are used to assess peptide-induced vesicle aggregation. The ability of gomesin to permeabilize the membrane is examined with fluorescence spectroscopy of the leakage of 5,6-carboxyfluorescein (CF). Vesicles coated with 3 mol % 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (PE-PEG) lipids are also investigated to assess the influence of peptide-induced vesicle aggregation in the activity of gomesin. The ITC and light scattering titrations are done in two ways: lipid into peptide and peptide into lipid injections. Although some differences arise between the two setups, the basic interaction of gomesin with anionic vesicles is preserved. A surface partition model combined with the Gouy-Chapman theory is put forward to fit the ITC results. The intrinsic binding constant of gomesin is found to be K ≈ 10(3) M(-1). The interaction of gomesin with anionic membranes is highly exothermic and enthalpy-driven. Binding of gomesin is virtually always accompanied by vesicle aggregation and changes in membrane permeability, leading to CF leakage. Addition of PE-PEG to the membrane strongly attenuates vesicle aggregation but does not significantly change the mode of action of gomesin. The results point to a strong interaction of gomesin with the membrane surface, causing membrane rupture without a deep penetration into the bilayer core.
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Tatiana M
authors.initials: TM
authors.lastname: Domingues
authors.forename: Bruno
authors.initials: B
authors.lastname: Mattei
authors.forename: Joachim
authors.initials: J
authors.lastname: Seelig
authors.forename: Katia R
authors.initials: KR
authors.lastname: Perez
authors.forename: Antonio
authors.initials: A
authors.lastname: Miranda
authors.forename: Karin A
authors.initials: KA
authors.lastname: Riske
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D002151:Calorimetry; D008958:Models, Molecular; D010316:Particle Size; D010713:Phosphatidylcholines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D023181:Antimicrobial Cationic Peptides; D010713:Phosphatidylcholines; D010743:Phospholipids; C415987:gomesin; C028694:1-palmitoyl-2-oleoylphosphatidylcholine