Fluorescence study on the interaction of a multiple antigenic peptide from hepatitis A virus with lipid vesicles

✍ Scribed by A. Ortiz; Y. Cajal; I. Haro; F. Reig; M. A. Alsina

• Publisher: Wiley (John Wiley & Sons)
• Year: 2000
• Tongue: English
• Weight: 158 KB
• Volume: 53
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/(sici)1097-0282(200005)53:6<455::aid-bip2>3.0.co;2-j

✦ Synopsis

The interaction of the multiple antigenic peptide MAP 4 VP3 with lipid membranes has been studied by spectroscopic techniques. MAP 4 VP3 is a multimeric peptide that corresponds to four units of the sequence 110 -121 of the capsid protein VP3 of hepatitis A virus. In order to evaluate the electrostatic and hydrophobic components on the lipid-peptide interaction, small unilamelar vesicles of different compositions, including zwitterionic dipalmitoylphosphatidylcholine (DPPC), anionic dipalmitoylphosphatidylcholine/phosphatidylinositol (DPPC : PI 9:1), and cationic dipalmitoylphosphatidylcholine/stearylamine (DPPC : SA 9.5:0.5), were used as membrane models. Intrinsic tryptophan fluorescence changes and energy transfer experiments show that MAP 4 VP3 binds to all three types of vesicles with the same stoichiometry, indicating that the electrostatic component of the interaction is not important for binding of this anionic peptide. Steady-state polarization experiments with vesicles labeled with 1,6-diphenyl-1,3,5-hexatriene or with 1-anilino-8-naphtalene sulphonic acid indicate that MAP 4 VP3 induces a change in the packing of the bilayers, with a decrease in the fluidity of the lipids and an increase in the temperature of phase transition in all the vesicles. The percentage of lipid exposed to the bulk aqueous phase is around 60% in intact vesicles, and it does not change upon binding of MAP 4 VP3 to DPPC vesicles, indicating that the peptide does not alter the permeability of the membrane. An increase in the amount of lipid exposed to the aqueous phase in cationic vesicles indicates either lipid flip-flop or disruption of the vesicles. Binding to DPPC vesicles occurs without leakage of entrapped carboxyfluorescein, even at high mol fractions of peptide. However, a time-dependent leakage is seen with