ASSEMBLY AND ANTIGENICITY OF HEPATITIS-B VIRUS CORE PARTICLES

Recent studies in Xenopus oocytes and other systems have led to an und erstanding of the HBV capsid, or core particle, assembly process. Nasc ent HBV core polypeptides rapidly dimerize. Accumulation of free dimer s to a signature concentration (similar to 0.8 mu M) then triggers a h ighly cooperative capsid assembly reaction. This dimer-to-capsid trans ition is accompanied by a switch from HBe to HBe antigenicity and appe ars to be nucleated by interaction between core protein and RNA: delet ion of a protamine-like RNA binding domain at the C-terminus of the co re protein markedly increases the concentration of dimers needed to dr ive capsid assembly. The simple assembly pathway seen for HBV capsids mirrors that of R17 bacteriophage.