PH-INDUCED DESTABILIZATION OF LIPID BILAYERS BY A PEPTIDE FROM THE VP3 PROTEIN OF THE CAPSID OF HEPATITIS-A VIRUS

The membrane destabilizing and fusogenic properties of the synthetic p eptide VP3(110-121), corresponding to an immunogenic sequence of the h epatitis A virus (HAV) VP3 capsid protein, were studied. By tryptophan fluorescence and acryalmide quenching it was demonstrated that the pe ptide binds liposomes of POPC-SM-DPPE (47 + 39 + 14) and POPC-SM-DPPE- DOTAP (40 + 33 + 12 + 15) and penetrates the membrane, at both neutral and acidic pH (POPC = 1-palmitoyl-2-oleoylglycero-sn-3-phosphocholine ; SM = sphingomyelin; DPPE = 1,2-dipalmitoylphosphatidylethanolamine; DOTAP = 1,2-dioleoyl-3-trimethylammoniumpropane) VP3(110-121) did not have membrane-destabilizing properties at neutral pH. Acid-induced des tabilization of the vesicles was demonstrated by fluorescence techniqu es and dynamic light scattering. VP3(110-121) induced aggregation of P OPC-SM-DPPE-DOTAP (40 + 33 + 12 + 15) vesicles, lipid mixing and leaka ge of vesicle contents, all consistent with fusion of vesicles. In POP C-SM-DPPE (47 + 39 + 14) vesicles, at acidic pH, VP3(110-121) induced membrane destabilization with leakage of contents but without aggregat ion of vesicles or lipid mixing. The peptide only showed fusogenic pro perties when bound to the vesicles at neutral pH before acidification to pH below 6.0, and no effect was seen if the peptide was added to ve sicles already set at acidic pH. These results may have physiological significance in the mechanism of infection of host hepatic cells by HA V.