INTERACTION OF A MULTIPLE ANTIGENIC PEPTIDE OF HEPATITIS-A VIRUS WITHMONOLAYERS AND BILAYERS OF ACIDIC, BASIC, AND ZWITTERIONIC PHOSPHOLIPIDS

The interaction of the synthetic multiple antigenic peptide construct MAP(4)-VP1 (11-25) with lipid membranes was studied by a combination o f spectroscopic and biophysical techniques. MAP(4)-VP1 showed an impor tant surface activity when spread in an air-water interface, indicativ e of an amphipatic conformation. Since this peptide has a net anionic charge, we studied the degree of interaction with model membranes of z witterionic dipalmitoylphosphatidylcholine (DPPC), anionic phosphatidy linositol (PI and DPPC/PI 9:1), or cationic stearylamine (SA and DPPC/ SA 9:1), MAP(4)-VP1 was readily soluble in aqueous buffer, yet spontan eously inserted from an aqueous subphase into cationic and zwitterioni c monolayers up to limiting pressures of 20-30 mN/m. The induced surfa ce pressure increases were in the order cationic > zwitterionic > anio nic monolayers. This indicates that the interaction is mainly driven b y electrostatic forces, although there is an important hydrophobic com ponent, responsible for the penetration in monolayers of neutral DPPC. Interaction of MAP(4)-VP1 with unilamellar vesicles of DPPC, DPPC/SA (9:1), and DPPC/PI (9:1) labeled with 1,6-diphenyl-1,3,5-hexatriene (D PH) or with 1-anilino-8-naphthalene sulfonic acid (ANS) was determined by changes in fluorescence polarization as a function of temperature, Results showed that the presence of the positively charged SA in the membrane strongly enhances the incorporation of MAP(4)-VP1 and that th e peptide increases the fluidity of the bilayer and decreases the temp erature of the phase transition. (C) 1998 Academic Press.